883. The MEATUSES are passages that extend backward, from the nostrils, into which are several openings. They are lined by a mucous membrane, called the pi-tu'i-ta-ry, or schneiderian, from Schneider, who first showed that the secretion of the nasal fossae proceeded from the mucous membrane, and not from the brain.

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882. What terms are applied to the spaces between these processes? What does fig. 135 represent? 883. Define the meatuses. By what are they lined?

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884. Upon the mucous membrane of the nasal passages, the olfactory nerve ramifies, and also a branch of the fifth pair of nerves. This membrane is of considerable extent in man; and in those animals whose sense of smell is very acute, it is still more extensive.



PHYSIOLOGY OF THE ORGANS OF SMELL.

885. The sense of smell enables us to discern the odor or scent of any thing. When substances are presented to the nose, the air that is passing through the nostrils brings the odoriferous particles of matter in contact with the filaments of the olfactory nerves, that are spread upon the membrane that lines the air-passages, and the impression is then transmitted to the brain.

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884. What nerves ramify upon this membrane? What is represented by fig. 136? 885-899. Give the physiology of the organs of smell. 885. How does the mind become sensible of odoriferous particles?

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886. This sense, with that of taste, aids man as well as the inferior animals, in selecting proper food, and it also gives us pleasure by the inhalation of agreeable odors. The sense of smell, like that of taste and touch, may be improved by cultivation. It likewise varies in different persons.

Observation. Sometimes this sense seems to possess a morbid degree of acuteness in respect to odors, which is highly inconvenient and even dangerous. With some individuals, the smell of certain fruits, flowers, cheese, &c., produce nausea and even convulsions.

887. In the inferior animals generally, the sense of smell is more acute than in man. Thus the bloodhound will track the hare over the ground for miles, guided only by the odor that it leaves in its flight. He also traces the progress of his master through thickly-crowded streets, distinguishing his footsteps from those of a thousand others, and amidst the odorous particles emanating from a thousand sources.

Observation. In some of the higher orders of the inferior animals, there is an astonishing acuteness of smell in regard to effluvia that come from living animals. To these animals, it possesses an importance in them far beyond what it has in man, by making them acquainted with the presence of their enemies or their prey, when the eye and ear are incapable of acting. It is related by travellers in Africa, that they were always apprised of lions in their vicinity during the night, by the moans and tremblings of their horses.

888. Smell is somewhat under the control of the will. That is, we have the power of receiving or rejecting odors that are presented; thus, if odors are agreeable, we inspire forcibly, to enjoy them; but, if they are offensive, our inspirations are more cautious, or we close our nostrils. This sense is likewise modified by habit; odors which, in the first instance, were very offensive, may not only become endurable, but even agreeable.

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886. What is the use of the sense of smell? Can this sense be improved by cultivation? What is said respecting this sense in some individuals? 887. What is said of this sense in the bloodhound? Mention an instance of astonishing acuteness of smell in some of the higher orders of animals. 888. Show that smell is somewhat under the control of the will.

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889. Acuteness of smell requires that the brain and nerve of smell be healthy, and that the membrane that lines the nose be thin and moist. Any influence that diminishes the sensibility of the nerves, thickens the membrane, or renders it dry, impairs this sense.

Observations. 1st. Snuff, when introduced into the nose, not only diminishes the sensibility of the nervous filaments, but thickens the lining membrane. This thickening of the membrane obstructs the passage of air through the nostrils, and thus obliges "snuff-takers" to open their mouths when they breathe.

2d. The mucous membrane of the nasal passages is the seat of chronic catarrh. This affection is difficult of removal, as remedial agents cannot easily be introduced into the windings of these passages. Snuff and many other articles used for catarrh, produce more disease than they remove.

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889. On what does acuteness of smell depend? What effect has snuff when introduced into the nose? What is said of chronic catarrh?

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CHAPTER XLIV.

SENSE OF VISION.

890. This sense contributes more to the enjoyment and happiness of man than any other of the senses. By it we perceive the form, color, volume, and position of objects that surround us. The eye is the organ of sight, or vision, and its mechanism is so wonderful, that it not only proves the existence of a great First Cause, but perhaps, more than other organs, the design of the Creator to mingle pleasure with our existence.

ANATOMY OF THE ORGANS OF VISION.

891. The apparatus of vision consists of the Op'tic Nerve, the Globe and Muscles of the eye, and its Protecting Organs.

892. The OPTIC NERVE arises by two roots from the central portion of the base of the brain. The two nerves approach each other, as they proceed forward, and some of the fibres of each cross to the nerve of the opposite side. They then diverge, and enter the globe of the eyes at their back part, where they expand, and form a soft, whitish membrane.

893. The GLOBE, or ball of the eye, is an optical instrument of the most perfect construction. The sides of the globes are composed of Coats, or membranes. The interior of the globe is filled with refracting Humors, or me'di-ums.

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890. Which sense contributes most to the enjoyment of man? What do we perceive by this sense? What is said of the mechanism of the eye? 891-916. Give the anatomy of the organs of vision. 891. Of what does the apparatus of vision consist? 892. Describe the optic nerve. 893. Describe the globe of the eye.

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894. The COATS are three in number: 1st. The Scle-rot'ic and Corn'e-a. 2d. The Cho'roid, Iris, and Cil'ia-ry processes. 3d. The Ret'i-na.

895 The HUMORS are also three in number: 1st. The A'que-ous, or watery. 2d. The Crys'tal-line, (lens.) 3d. The Vit're-ous, or glassy.



896. The SCLEROTIC COAT is a dense, fibrous membrane and invests about four fifths of the globe of the eye. It gives form to this organ, and serves for the attachment of the muscles that move the eye in various directions. This coat, from the brilliancy of its whiteness, is known by the name of "the white of the eye." Anteriorly, the sclerotic coat presents a bevelled edge, which receives the cornea in the same way that a watch-glass is received by the groove in its case.

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894. Name the coats of the eye. 895. Name the humors of the eye. Explain fig. 137. 896. Describe the sclerotic coat.

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897. The CORNEA is the transparent projecting layer, that forms the anterior fifth of the globe of the eye. In form, it is circular, convexo-concave, and resembles a watch-glass. It is received by its edge, which is sharp and thin, within the bevelled border of the sclerotic, to which it is firmly attached. The cornea is composed of several different layers; its blood-vessels are so small that they exclude the red particles altogether, and admit nothing but serum.

898. The CHOROID COAT is a vascular membrane, of a rich chocolate-brown color upon its external surface, and of a deep black color within. It is connected, externally, with the sclerotic, by an extremely fine cellular tissue, and by the passage of nerves and vessels; internally, it is in contact with the retina. The choroid membrane is composed of three layers. It secretes upon its internal surface a dark substance, called pig-ment'um ni'grum, which is of great importance in the function of vision.

899. The IRIS is so called from its variety of color in different persons. It forms a partition between the anterior and posterior chambers of the eye, and is pierced by a circular opening, which is called the pu'pil. It is composed of two layers. The radiating fibres of the anterior layer converge from the circumference to the centre. Through the action of these radiating fibres the pupil is dilated. The circular fibres surround the pupil, and by their action produce contraction of its area. The posterior layer is of a deep purple tint, and is called u-ve'a, from its resemblance in color to a ripe grape.

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How are this coat and the cornea united? 897. Describe the cornea. 898. What is the color of the external surface of the choroid coat? Of the internal? How is it connected externally? How internally? What does this membrane secrete upon its internal surface? 899. Describe the iris. Of how many layers of fibres is the iris composed? What is the function of the radiating fibres? Of the circular?

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900. The CILIARY PROCESSES consist of a number of triangular folds, formed, apparently, by the plaiting of the internal layer of the choroid coat. They are about sixty in number. Their external border is continuous with the internal layer of the choroid coat. The central border is free, and rests against the circumference of the crystalline lens. These processes are covered by a layer of the pigmentum nigrum.



901. The RETINA is composed of three layers: The external; middle, or nervous; and internal, or vascular. The external membrane is extremely thin, and is seen as a flocculent film, when the eye is suspended in water. The nervous membrane is the expansion of the optic nerve, and forms a thin, semi-transparent, bluish-white layer. The vascular membrane consists of the ramifications of a minute artery and its accompanying vein. This vascular layer forms distinct sheaths for the nervous papillae, which constitute the inner surface of the retina.

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900. How are the ciliary processes formed? What does fig. 138 exhibit? 901. Of how many layers is the retina composed? Describe the external layer. The nervous layer.

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902. The AQUEOUS HUMOR is situated in the anterior and posterior chambers of the eye. It is an albuminous fluid, having an alkaline reaction. Its specific gravity is a very little greater than distilled water. The anterior chamber is the space intervening between the cornea, in front, and the iris and pupil, behind. The posterior chamber is the narrow space, less than half a line in depth, bounded by the posterior surface of the iris and pupil, in front, and by the ciliary processes and crystalline lens, behind. The two chambers are lined by a thin layer, the secreting membrane of the aqueous humor.

903. The CRYSTALLINE HUMOR, or lens, is situated immediately behind the pupil, and is surrounded by the ciliary processes. This humor is more convex on the posterior than on the anterior surface, and, in different portions of the surface of each, the convexity varies from their oval character. It is imbedded in the anterior part of the vitreous humor, from which it is separated by a thin membrane, and is invested by a transparent elastic membrane, called the capsule of the lens. The lens consists of concentric layers, disposed like the coats of an onion. The external layer is soft, and each successive one increases in firmness until the central layer forms a hardened nucleus. These layers are best demonstrated by boiling, or by immersion in alcohol, when they separate easily from each other.

Observations. 1st. The lens in the eye of a fish is round, like a globe, and has the same appearance, when boiled, as the lens of the human eye.

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The vascular layer. 902. Where is the aqueous humor situated? What part of the eye is called the anterior chamber? The posterior chamber? With what are the chambers lined? 903. Where is the crystalline humor situated? With what is it surrounded? Of what does the lens consist? How are these layers best demonstrated? What is produced when the lens, or its investing membrane, is changed in structure?

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2d. When the crystalline lens, or its investing membrane, is changed in structure, so as to prevent the rays of light passing to the retina, the affection is called a cataract.



904. The VITREOUS HUMOR forms the principal bulk of the globe of the eye. It is an albuminous fluid, resembling the aqueous humor, but is more dense, and differs from the aqueous in this important particular, that it has not the power of re-producing itself. If by accident it is discharged, the eye is irrecoverably lost; while the aqueous humor may be let out, and will be again restored. It is enclosed in a delicate membrane, called the hy'a-loid, which sends processes into the interior of the globe of the eye, forming the cells in which the humor is retained.

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904. Describe the vitreous humor. How does this humor differ from the aqueous? What membrane encloses the vitreous humor?

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Observation. The structure of this organ can be seen by first freezing the eye of a sheep or an ox; it then can be cut in various directions, and each part separately examined.

905. The MUSCLES of the eye are six in number. They are attached, at one extremity, to the bones of the orbit behind the eye; at the other extremity, they are inserted by broad, thin tendons, near the junction of the cornea with the sclerotic coat. The white, pearly appearance of the eye is caused by these tendons.



Observation. If the external muscle is too short, the eye is turned out, producing the "wall eye." If the internal muscle is contracted, the eye is turned inward toward the nose. It is then called a "cross eye."

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905. How many muscles has the eye? Give their attachments. What causes the pearly appearance of the eye? What does fig. 140 represent? What is the effect if the external muscle is contracted? The internal muscle?

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906. The PROTECTING ORGANS are the Or'bits, Eyebrows, Eyelids, and Lach'ry-mal Apparatus.

907. The ORBITS are deep, bony sockets, in which the globes of the eyes are situated. They have the form of a cone, the base of which is open and directed forward. The bottom of the orbits is pierced by a large hole which gives passage to the optic nerve. These cavities are lined with a thick cushion of fat, in order that the eyes may move in all directions, with perfect freedom and without friction.

908. The EYEBROWS are two projecting arches of integument, covered with short, thick hairs, which form the upper boundary of the orbits. The eyebrows are so arranged that they prevent the moisture that accumulates on the forehead, in free perspiration, from flowing into the eye, and also shade these organs from too vivid light.

909. The EYELIDS are two movable curtains placed in front of the eye. They have a delicate skin on the outside, muscular fibres beneath, and a narrow cartilage on their edges, which tends to preserve the shape of the lid. Internally, they are lined by a smooth membrane, which is reflected over the front of the eye upon the sclerotica. This membrane is called the con-junc-ti'va. It secretes the fluid that moistens and lubricates the eye, and which causes the eyelids to open and shut without friction.

Observation. When the portion of this membrane that is reflected over the globe of the eye, is inflamed, there is frequently a deposition of whitish material, called lymph. This accounts for the films, opacities, and white spots seen upon the eye after the inflammation has subsided.

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906. Name the protecting organs of the eye. 907. Describe the orbits. How are the movements of the eye facilitated? 908. Describe the eyebrows. What does this arrangement prevent? 909. Describe the eyelids. What is the use of the conjunctiva? How are the white spots frequently seen upon the eye accounted for?

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910. There are found several small glands on the internal surface of the cartilage, which have the appearance of parallel strings of pearls. They open by minute apertures upon the edges of the lids. The secretion from these glands prevents the edges of the eyelids from being united during sleep.

911. The edges of the eyelids are furnished with a triple row of long, thick hairs, called eyelashes, which curve upward from the upper lid, and downward from the lower, so that they may not interlace with each other in the closure of the eyelids. These appendages of the eye, by closing, not only protect it from moisture, but from dust, particularly during sleep. They likewise, by their movements in opening and shutting, spread the lubricating fluid equally over the eye.

912. The LACHRYMAL APPARATUS, which secretes the tears, consists of the Lachrymal Gland with its ducts, Lachrymal Canals, and the Nasal Duct.

913. The LACHRYMAL GLAND is situated at the upper and outer angle of the orbit. It is about three quarters of an inch in length, flattened and oval in shape, and occupies a depression in the orbital plate of the frontal bone. Ten or twelve small ducts pass from this gland, and open upon the upper eyelid, where they pour upon the conjunctiva the lachrymal fluid, or tears. This secretion is maintained while we are asleep, as well as when we are awake. The eye from this cause is kept constantly moist.

914. The LACHRYMAL CANALS commence at minute openings upon the free borders of each eyelid, near the internal angle of the eye, by two small orifices, called punc'ta lach-ry-ma'li-a, (tear points.) Each of these points communicate with the sac at the upper part of the nasal duct.

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910. What are found on the internal surface of the cartilage of the eyelids? Where do they open, and what is their use? 911. With what are the edges of the eyelids furnished? What are their uses? 912. Of what does the lachrymal apparatus consist? 913. Describe the lachrymal gland. How many ducts pass from this gland, and what do they convey to the eye? Why is the eye constantly moist? 914. Where do the lachrymal canals commence?

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915. The NASAL DUCT is a short canal, about three quarters of an inch in length, directed downward and backward to the inferior channel of the nose, where it terminates by an expanded orifice.



916. The fluid (tears) secreted by the lachrymal gland, is conveyed to the eye by the small ducts before described. It is then imbibed by the puncta lachrymalia, and carried by the lachrymal canals into the lachrymal sac, from which it is passed to the nasal cavities by the nasal ducts.

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What are they called? With what do they communicate? 915. Describe the nasal duct. 916. How are the tears conveyed from the lachrymal gland to the nose?

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CHAPTER XLV.

PHYSIOLOGY OF THE ORGANS OF VISION.

917. To comprehend the theory of vision, it is not sufficient to know the structure of the eye. We must be familiar with some of the properties of a subtile fluid, which is constantly emanating from all luminous bodies, called light.

918. It is the province of natural philosophy, rather than physiology, to enter minutely upon the properties of light. It may be observed, however, that, when light passes through any medium of the same density, the rays are in straight lines; but, when it passes from one medium into another of different density, it is refracted, or turned from a straight course, unless it strikes the medium in a perpendicular direction—then light passes through without a change of direction.

919. When a ray of light meets with a body, it either passes through it, or is reflected by it, or it may be absorbed. Again, in proportion as the rays of light become distant from the body from which they emanate, they diverge one from the other. In accordance with the laws of optics, the rays of light, in passing through an optical instrument like the eye, must cross each other, and thus produce an inverted image of the object from which the rays proceed. With the general view of the structure of the eye, we will now examine the use of each part in the function of vision.

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917-933. Give the physiology of the organs of vision. 917. What is necessary in order to understand the theory of vision? 918. When light passes through a medium of the same density, in what direction will be its rays? Of a different density? What exception? 919. When light meets with a body, what takes place? What is said in reference to rays of light in passing through the eye?

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920. The sclerotic coat not only gives form to the body of the eye, but protection to the interior and more delicate parts. The choroid coat seems to be chiefly composed of a tissue of nerves and minute blood-vessels; the latter give nourishment to the different parts of the eye. One of the uses of this coat is, to absorb the rays of light immediately after they have passed through the retina. This is effected by the black pigment that lines its inner surface. Were it not for this provision, light would be too intense, and vision indistinct.

Observation. In albinos, where there is an absence of the black pigment, the rays of light traverse the iris, and even the choroid coat, and so overwhelm the eye with light, that their vision is quite imperfect, except in the dimness of evening, or at night. In the manufacture of optical instruments, care is taken to color their interior black, for the same object, namely, the absorption of scattered rays.

921. The iris, by means of its powers of expansion and contraction, regulates the quantity of light admitted through the pupil. If the iris is thin, and the rays of light pass through its substance, they are immediately absorbed by the uvea, and, if that layer be insufficient, they are taken up by the black pigment of the choroid coat.

Observation. When we look toward the bottom of the eye, the pupil appears like a black spot, instead of an opening. This is caused by seeing the black pigment through the retina and humors of the eye.

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920. What is the use of the sclerotic coat? Of what is the choroid coat chiefly composed? What is the use of this coat? How is it effected? What is said of albinos? What care is taken in the manufacture of optical instruments? 921. What is the use of the iris? When we look toward the bottom of the eye, why does the pupil look like a black spot, instead of an opening?

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922. The cornea, and the aqueous, crystalline, and vitreous humors, are transparent; so that rays of light traverse these parts of the eye, and fall upon the retina. The office of these humors and the cornea is to refract the rays of light in such proportion as to direct the image in the most favorable manner upon the retina.

923. The office of the retina is to receive the impression of the rays of light which leave an object at which we look, and it is upon it that a small but very clear image of that object is formed. The impression thus produced by the reflected light is transmitted by the optic nerve to the brain, which receives the sensation. This constitutes vision.

924. The optic nerve has but one function, that of sight. Sensibility is conferred on this organ by a large branch from the fifth pair of nerves, which ramifies upon the different parts of the eye and its appendages. These parts, however, receive some nervous filaments from the seventh pair.

Observations. 1st. The large number of sensitive nervous filaments renders the visual organ very impressible to bodies that cause irritation, as dust, or intense light. This compels us to use due care to shield the eye from the influence of agents that would impair or destroy vision.

2d. Although particles of dust, when in contact with the delicate parts of the eye, induce severe pain, yet these parts may be cut in surgical operations, and the patient's sufferings are not as great as when an incision is made in the skin to remove a small tumor.

925. Different degrees of density, as already mentioned, modify the refractory power of any transparent medium. It is found, on examination, that the cornea, the vitreous, the crystalline, and the aqueous humors, have each, severally, various degrees of density: and that the crystalline lens, at its circumference, is less dense than at its centre. These circumstances modify the direction of the refraction of the rays of light, in their passage from the cornea to the retina.

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922. What is the use of the cornea, aqueous, crystalline, and vitreous humors? 923. What is the office of the retina? 924. What is the function of the optic nerve? How is sensibility conferred on this organ? Give the 1st observation in this connection. The 2d observation.

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926. The refracting powers of the plane, convex, concave, plano-convex, plano-concave, and concavo-convex lenses,[22] are different. The cornea and aqueous humors are convexo-concave, the vitreous humor is concavo-convex, while the crystalline humor is a convexo-convex medium. (Fig. 139.)

[22] The refracting character of differently-formed lenses is illustrated in the works on Natural Philosophy, to which the pupil is referred.



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925. Have the cornea and the humors of the eye different degrees of density? What is said of the crystalline lens? What effect has the different density of the parts of the eye upon the light admitted to this organ? 926. What kind of lenses do the humors exhibit? 927. What modifies the refracting powers of transparent mediums? How does this principle apply to the humors of the eye?

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927. The different degrees of convexity or concavity also modify the refracting character of transparent mediums. The crystalline lens is of different degrees of convexity on its two sides. The convex surfaces of the aqueous and vitreous humors are segments of circles, of different diameters from their concave surfaces. (Fig. 139.) All these circumstances still further influence the refracting character of the visual organ. The achromatic arrangement of the transparent refracting mediums of the eye, remedies the aberration of refraction in the different portions of the eye.

928. Again, the refracting power of lenses is modified by their convexity or concavity. The more convex a lens is, the shorter the distance from the refracting medium, where the different refracted rays converge to a focus. To adapt the eye to view objects at different distances, requires a change in the refracting power of some of the transparent mediums of the eye.

929. Both surfaces of the crystalline lens are oval, not spherical, and the refraction of the rays of light is mainly effected in this portion of the eye. Change the inclination of this lens, so that different portions of its anterior surface shall be directly behind the pupil, and its refracting power is increased or diminished, as the surface presented is more or less convex.

930. To view objects at a distance, a less convex lens is needed than in examining articles very near the eye; and this organ, from its structure, has the power of adaptation to different distances. It is supposed that the muscular substance of the ciliary body and processes changes, by its contraction, the inclination of the crystalline lens. Without this, or some other adapting power, a picture of objects at different distances would not be formed upon the retina, and the vision of every person would be defective, except in reference to objects at certain definite distances from the eye.

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928. What modifies the refracting power of lenses? What is necessary to adapt the eye to view objects at different distances? 929. Where is the refraction of the rays of light mainly effected? 930. When we view objects at a distance, what kind of lens is required? Has the eye the power of adapting itself to different distances? How is it effected?

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Observation. It is well known that a separate image is formed on each eye, and, if they are not in the same direction, the objects will appear double. This is proved by pressing one eye, so that the rays of light cannot enter it in the same direction as they do in the other; consequently, the vision is double.

931. By the action of the muscles of the eye, it is turned in different directions, so that objects can be examined upon each side, as well as in front, without turning the body. By the slight or intense action of the straight muscles, the eye is more or less compressed, and the form of the globe is changed, together with the relative positions of the different humors. This modification also adapts the eye to view objects at different distances.



Observation. If the eye is fixed for a time on some object which is distinguished with difficulty, there is a painful sensation, similar to that experienced by other muscles of the body when used too long. This is called "straining the eye."

932. When the refraction of the rays of light is too great, as in over-convexity of the cornea, or the crystalline lens, or the vitreous humor, or all of them, the image is formed a little in front of the retina. Persons thus affected cannot see distinctly, except at a very short distance. This infirmity is called near, or short-sightedness. This defect is in a great measure obviated by the use of concave glasses, which scatter the luminous rays, and thus counterbalance the too strong refracting force of the eye.

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What does fig. 143 represent? 931. Why can we see objects at the side as well as in front of the eye, without turning the body? What is the effect when the eye is fixed on an object that is indistinctly seen?

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933. When the different parts of the eye are not sufficiently convex, the image is formed beyond the retina, and thus only distant objects are distinctly seen. This defect is called long-sightedness. The feebleness in the refracting power of the eye may be caused by disease; but usually it is a consequence of old age, and is remedied by wearing spectacles with convex glasses.

HYGIENE OF THE ORGANS OF VISION.

934. The eye, like other organs of the body, should be used, and then rested. If we look intently at an object for a long time, the eye becomes wearied, and the power of vision diminished. The observance of this rule is particularly needful to those whose eyes are weak, and predisposed to inflammation. On the contrary, if the eye is not called into action, its functions are enfeebled.

935. Sudden transitions of light should be avoided. The iris enlarges or contracts, as the light that falls upon the eye is faint or strong; but the change is not instantaneous. Hence the imperfect vision in passing from a strong to a dim light, and the overwhelming sensation experienced on emerging from a dimly-lighted apartment to one brilliantly illuminated. A common cause of am-aur-o'sis, or paralysis of the retina, is, using the eye for a long time in a very intense light.

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932. What is short-sightedness? How is the defect remedied? 933. What is long-sightedness? How is the defect remedied? 934-942. Give the hygiene of the organs of vision. 934. Do the same principles apply to the use of the eye as to other organs? What is the effect if the eye is fixed intently on an object for a long time? What results if the eye is not called into action? 935. Why should sudden transitions of light be avoided?

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Note. Let the anatomy and physiology of the eye be reviewed from figs. 139 and 143, or from anatomical outline plate No. 10.

936. Long-continued oblique positions of the eye should be avoided, when viewing objects. If the eye is turned obliquely for a long time in viewing objects, it may produce an unnatural contraction of the muscle called into action. This contraction of the muscle is termed stra-bis'mus, or cross-eye. The practice of imitating the appearance of a person thus affected, is injudicious, as the imitation, designed to be temporary, may become permanent.

Observation. The vision of a "cross-eye" is always defective. In general, only one eye is called into action, in viewing the object to which the mind is directed. This defect can be remedied by a surgical operation, which also corrects the position of the eye.

937. Children should be trained to use the eye upon objects at different distances. This is necessary, in order that the vision may be correct when objects at various distances are viewed. Any action unnatural to the muscles, if frequently repeated, may and will modify the character and action of the parts so operated upon. If a limb, as the arm, be kept flexed for a long time, one set of muscles will be relaxed and elongated, and another will be shortened, and its contractile power will be increased. The same principle is true of the eye.

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What causes palsy of the retina? 936. Why should we avoid oblique positions of the eye in viewing objects? What is said of the practice of imitating persons thus affected? What is said in reference to the vision of a "cross-eye"? 937. Why should children be trained to use the eye upon objects at different distances? What is the effect if an unnatural action of the muscles is frequently repeated? Does the same principle apply to the eye?

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938. In viewing objects very near the eye, the ciliary processes are called into action to produce a proper inclination of the crystalline lens, so that the rays of light may be properly refracted to form a perfect image on the retina. In looking at objects at a great distance, the ciliary processes are called into a different action, to produce a different inclination of the lens. Let either of these actions be repeated, again and again, for weeks and months, and they will become natural, and the acquired inclination will be permanent.

939. From the preceding principle, a person becomes short or long sighted, as the objects to which the eye is usually directed are near or remote. This is one reason why scholars, watchmakers, and artisans, who bring minute objects near the eye to examine them, are short-sighted, and why hunters and sailors, who are habituated to view objects at a distance, are long-sighted.

Observation. In the management of children, whether in the nursery or school-room, it is very important that their books, or articles upon which they may labor, should be held at an appropriate distance from the eye. Were this attended to by the parent or instructor, we should not see so many persons with defective vision.

940. Cleanliness, as well as the health of the eye, require that it be bathed every morning with pure water, either cold or tepid, accompanied with as little rubbing or friction as possible. In all instances, the secretion from the lachrymal glands, that sometimes collects at the angle of the eye, should be removed, as it contains saline matter.

941. When small particles, or dust, get upon the eye, they produce much inconvenience, which is often increased by harsh attempts to remove them. The individual should be placed before a strong light, the lids held open with one hand, or by another person, and the particles removed with the corner of a fine linen or silk handkerchief.

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938. What is the effect of repeatedly using the eye in one direction? 939. Why are artisans and scholars generally short-sighted? Why are sailors and hunters long-sighted? How can defective vision in a great degree be prevented? 940. What reasons are there for bathing the eye? 941. How can dust and other small particles be removed from the eye?

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942. Sometimes the substance is concealed under the upper eyelid, and it may then be exposed by turning back the lid in the following manner: Take a knitting-needle, or small, slender piece of stick, which is perfectly smooth, and place it over the upper lid, in contact with, and just under the edge of the orbit; then, holding it firmly, seize the eyelashes with the fingers of the disengaged hand, and gently turn the lid back over the stick or needle. The inner side of the lid can then be examined, and any substance removed that may have been there concealed. Too many trials ought not to be made, if unsuccessful, as much inflammation may be induced; but a surgeon should be consulted as soon as possible.

Observation. Eyestones ought never to be placed in the eye, as they often cause more pain and irritation than the evil which they are intended to remedy.

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942. How removed from the upper eyelid? Why should not eyestones be used?

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CHAPTER XLVI.

THE SENSE OF HEARING.

943. The sense of hearing is next in importance to that of vision. Through this sense we are enabled to perceive sounds, that not only subserve to our comfort and pleasure, but are instrumental in promoting our intellectual enjoyments. The organ of hearing, or the ear, is one of the most complicated in the human body.

ANATOMY OF THE ORGANS OF HEARING.

944. The EAR is composed of three parts: 1st. The External Ear. 2d. The Tym'pan-um, or middle ear. 3d. The La'by-rinth, or internal ear.

945. The EXTERNAL EAR is composed of two parts: The Pin'na, (pavilion of the ear,) and the Me-a'tus Aud-it-o'ri-us Ex-ter'nus, (auditory canal.)

946. The PINNA is a cartilaginous plate which surrounds the entrance of the auditory canal. It presents many ridges and furrows, arising from the folds of the cartilage that form it.

Observation. The pinna, in many animals, is movable; in those that pursue their prey, it is generally directed forward; in timid animals, as the hare and rabbit, it is directed backward. In man, this part is but slightly under the control of the will.

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943. What is said of the importance of hearing? Is the ear complicated in its structure? 944-962. Give the anatomy of the organs of hearing. 944. Of how many parts is the ear composed? Name them. 945. Give the parts of the external ear. 946. Describe the pinna. What is said in reference to the pinna of many animals?

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947. The MEATUS AUDITORIUS is a canal partly cartilaginous, and partly bony, about an inch in length, which extends inward from the pinna to the Mem'bra-na Tym'pan-i, (drum of the ear.) It is narrower in the middle than at the extremities. It is lined by an extremely thin pouch of cuticle, which, when withdrawn, after maceration, preserves the form of the canal. Some stiff, short hairs are also found in the interior of the channel, which stretch across the tube, and prevent the ingress of insects. Beneath the cuticle are a number of small follicles, which secrete the wax of the ear.



948. The MEMBRANA TYMPANI is a thin, semi-transparent membrane, of an oval shape. It is about three eighths of an inch in diameter, and is inserted into a groove around the circumference of the meatus, near its termination. This membrane is placed obliquely across the area of that tube. It is concave toward the meatus, and convex toward the tympanum.

949. The TYMPANUM consists of an irregular bony cavity, situated within the temporal bone. It is bounded externally by the membrana tympani; internally by its inner wall; and in its circumference by the petrous portion of the temporal bone and mastoid cells. The tympanum contains four small bones, called the os-sic'u-la au-di'tus. These are named separately, the mal'le-us, in'cus, sta'pes, and or-bic'u-lar.

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947. What is the meatus auditorius? What is found in this canal? What is their use? Where is the wax of the ear secreted? 948. Describe the membrana tympani. 949. Where is the tympanum situated?

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950. There are ten openings in the middle ear; five large and five small. The larger openings are, the Me-a'tus Aud-it-o'ri-us Ex-ter'nus, Fe-nes'tra O-va'lis, (oval window,) Fe-nes'tra Ro-tun'da, (round window,) Mas'toid Cells, and Eu-sta'chi-an Tube.



951. The FENESTRA OVALIS is the opening of communication between the tympanum and the vestibule. It is closed by the foot of the stapes, or bone of the ear, and by the lining membrane of both cavities.

952. The FENESTRA ROTUNDA serves to establish a communication between the tympanum and the cochlea. it is closed by a proper membrane, as well as by the lining of both cavities.

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What does this cavity contain? 950. How many openings in the tympanum? Explain fig. 145. 951. Describe the fenestra ovalis. 952. The fenestra rotunda.

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953. The MASTOID CELLS are very numerous, and occupy the whole of the interior of the mastoid process of the temporal bone, and part of the petrous bone. They communicate, by a large, irregular opening, with the upper and posterior circumference of the tympanum.



954. The EUSTACHIAN TUBE is a canal of communication, extending obliquely between the pharynx and the anterior circumference of the tympanum. In structure it is partly fibro-cartilaginous and partly bony. It is broad and expanded at its pharyngeal extremity, and narrow and compressed at the tympanum.

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953. Where are the mastoid cells? Explain fig. 146. 954. Describe the Eustachian tube.

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955. The small openings of the middle ear are for the entrance and exit of the chorda tympani, (a small nerve that crosses the tympanum,) and for the exit of the muscles that act upon the membrana tympani and bones of the ear.

956. The LABYRINTH consists of a membranous and a bony portion. The bony labyrinth presents a series of cavities which are channelled through the substance of the petrous bone. It is situated between the cavity of the tympanum and the Aud'it-o-ry Nerve. The labyrinth is divided into the Ves'ti-bule, Sem-i-cir'cu-lar Canals, and Coch'le-a.

957. The VESTIBULE is a small, three-cornered cavity, situated immediately within the inner wall of the tympanum.

958. The SEMICIRCULAR CANALS are three bony passages which communicate with the vestibule, into which two of them open at both extremities, and the third at one extremity.

959. The COCHLEA forms the anterior portion of the labyrinth. It consists of a bony and gradually tapering canal, about one and a half inches in length, which makes two turns and a half, spirally, around a central axis, called the mo-di'o-lus. The modiolus is large near its base, where it corresponds with the first turn of the cochlea, and diminishes in diameter toward its extremity.

960. The interior of the canal of the cochlea is partially divided into two passages, by means of a bony and membranous plate. At the extremity of the modiolus, the two passages communicate with each other. At the other extremity, one opens into the vestibule; the other into the tympanum, by the foramen rotundum. The internal surface of the bony labyrinth is lined by a fibro-serous membrane.

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955. What passes through the small openings of the middle ear? 956. Of what does the labyrinth consist? Give the parts of the internal ear. 957. Describe the vestibule. 958. What is said of the semicircular canals? 959. Why is the cochlea so called? Of what does it consist? 960. How is the interior of the canal of the cochlea divided? Where do they communicate with each other?

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961. The membranous labyrinth is smaller in size, but a perfect counterpart, with respect to form, of the bony vestibule, cochlea, and semicircular canals. Within this labyrinth are two small, elongated sacs, which are filled with a fluid.



962. The AUDITORY NERVE enters the temporal bone upon its internal surface, and divides into two branches, at the bottom of the cavity of the internal ear. These branches enter the structure of the elongated sacs and membranous labyrinth, radiating in all directions, and finally, they terminate upon the inner surface of the membrane, in minute papillae, resembling those of the retina.

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By what is the internal labyrinth lined? 961. Describe the membranous labyrinth. What does fig. 147 represent? 962. Where does the auditory nerve enter and divide? Where do the branches of the auditory nerve enter and terminate?

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CHAPTER XLVII.

PHYSIOLOGY OF THE ORGANS OF HEARING.

963. HEARING is that function by which we obtain a knowledge of the vibratory motions of bodies, which constitute sounds. The precise function of all the different parts of the ear is not known.

964. The function of that part of the external ear which projects from the head is to collect sounds and reflect them into the meatus.

965. The membrana tympani serves to facilitate the transmission of sounds, and also to moderate their intensity. It is so arranged that it can be relaxed or tightened.

Observation. This membrane, when healthy, has no opening; and it must be apparent that the apprehension which is often expressed, that insects will penetrate further, is groundless. The pain is owing to the extreme sensibility of the membrana tympani.

966. The supposed office of the tympanum is to transmit the vibrations made on the membrana tympani to the internal ear. This is effected by the air which it contains, and by the chain of small bones that are enclosed in this cavity.

967. The use of the Eustachian tube is to admit air into the tympanum, which renders the pressure on both sides equal, and thus its membrane is kept in a proper state of tension.

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963-971. Give the physiology of the organs of hearing. 963. What is hearing? Are the precise functions of the different parts of the ear known? 964. What is the function of the external ear? 965. Of the membrana tympani? What observation in reference to this membrane? 966. What is the supposed office of the middle ear? 967. What is the use of the Eustachian tube?

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Observation. When near a cannon, or a field-piece, about being discharged, by opening the mouth the impression upon the auditory nerve will be diminished, and the unpleasant sensation lessened. This is the result of the air in the middle ear escaping through the Eustachian tube, when the vibrations of the membrana tympani are violent.



968. But little is known of the functions of the internal ear; its parts are filled with a watery fluid, in which the filaments of the auditory nerve terminate.

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What observation in this connection? 968. What is the function of the internal ear?

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969. Many of the parts just enumerated aid in hearing, but are not absolutely essential to this sense. But if the vestibule and auditory nerve are diseased or destroyed, no sound is then perceived. If this sense is destroyed in early life, the person also loses the power of articulating words. Hence a man born deaf is always dumb.

970. The transmission of sound through the different parts of the ear will now be explained by aid of fig. 148. The vibrations of air are collected by the external ear, and conducted through the tube (1) to the membrana tympani, (2.) From the membrane vibrations pass along the chain of bones, (3, 4, 5.) The bone 5 communicates with the internal ear, (7, 8, 9, 10, 11, 11, 11, 12, 12, 12.) From the internal ear the impression is transmitted to the brain by the nerve, (13.)

971. The auditory nerve, like the optic, has but one function, that of special sensibility. The nerves which furnish the ear with ordinary sensibility, proceed from the fifth pair.

HYGIENE OF THE ORGANS OF HEARING.

972. Hearing, like the other senses, is capable of very great improvement. By cultivation, the blind are enabled to judge with great accuracy the distance of bodies in motion, and even the height of buildings. It is also capable of improvement when all the other senses are perfect. Thus the Indian will distinguish sounds that are inaudible to the white man.

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969. What parts of the ear are essential in order to hear sounds? What follows loss of hearing? 971. What is the office of the auditory nerve? What nerves convey ordinary sensibility to the ear? 972-978. Give the hygiene of the organs of hearing. 972. Is this sense capable of improvement? How does this sense aid the blind? Is it also capable of improvement when all the other senses are perfect? In whom is this illustrated?

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Note. Let the anatomy and physiology of the organs of hearing be reviewed, from fig. 148, or from anatomical outline plate No. 10.

973. Acute hearing requires perfection in the structure and functions of the different parts of the ear, and that portion of the brain from which the auditory nerve proceeds. Deafness is by no means unfrequent. We will now advert to some of the common causes of imperfect hearing.

974. The structure or functional action of the brain may be deranged by inflammation, by compression, or by debility, and produce deafness. The first is seen during inflammatory affections of the brain, and in fevers; the second is seen in accidental injuries of the head; the third is seen in old age, and after severe diseases of the head, and fevers. In these cases, applications to, and operations upon, the ear do no good. The only remedy is to remove, if possible, the diseased condition of the brain.

975. Imperfect hearing may be produced by the destruction of the membrana tympani, or removal of the bones of the ear, or the parts within the labyrinth. In these instances, medical treatment is of no avail, as the destroyed parts cannot be restored.

976. Hearing may be rendered defective by a diminution of the vibratory character of the membrana tympani. This may result from a thickening of this membrane, or from an accumulation of wax upon its outer surface. The increased thickness is usually the result of inflammation, either acute or chronic. The proper treatment is such as is efficient to remove inflammatory action.

Observations. 1st. The introduction of heads of pins into the ear is a frequent cause of chronic inflammation of the membrana tympani. Hence this practice should never be adopted, and if acquired, should be abandoned.

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973. On what does acute hearing depend? 974. State effects on the hearing in some conditions of the brain. How relieved? 975. Of the effect on hearing when the bones of the ear or the labyrinth are destroyed? Is medical treatment of any avail? 976. What conditions of the drum of the ear may impair hearing? How relieved? What is said of the introduction of pins to cleanse the ear?

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2d. The accumulations of viscid wax may be softened by dropping some animal oil into the ear, and then removing it by ejecting warm soap suds a few hours subsequent to the use of the oil. This may be repeated for several successive days.

977. Hearing may be impaired by obstruction of the Eustachian tube. The closure of this canal diminishes the vibratory character of the air within the tympanum, in the same manner as closing the opening in the side of a drum. For the same reason, enlarged tonsils, inflammation and ulceration of the fauces and nasal passages during and subsequent to an attack of scarlet fever, and the inflammation attending the "sore throat" in colds, are common causes of this obstruction.

978. The treatment of such cases of defective hearing, is to have the tonsils, if enlarged, removed by a surgeon; for the inflammation and thickening of the parts remedial means should be applied, directed by a skilful physician. The nostrums for the cure of deafness are generally of an oleaginous character, and may be beneficial in cases of defective hearing caused by an accumulation of wax upon the drum of the ear, but in this respect they are no better than the ordinary animal oils.

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What is the remedy where there is an accumulation of wax? 977. What is the effect on hearing if the Eustachian tube is obstructed? 978. What is the treatment when deafness is caused by inflammation or ulceration the fauces? What is said of the nostrums used for deafness?

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CHAPTER XLVIII

MEANS OF PRESERVING THE HEALTH.[23]

[23] It is advised, that a thorough review of the hygiene of the preceding chapters be given from the suggestions contained in this.

979. Our bodies are constituted in harmony with certain laws, and every person should learn these, in order to regulate his actions and the performance of his duties, so that health may be unimpaired, and the power of enjoyment, activity, and usefulness continue while life lasts.

980. It is a law of the bones and the muscles, that they should either be used in some vocation, or called into action by some social play and active sport.

981. All admit that food is necessary to sustain life; and unless it be of a proper quality, taken in proper quantities, and at proper times, the functions of the digestive organs will be deranged, and disease produced.

982. Pure air is essential to the full enjoyment of health. The impure air of unventilated rooms may be breathed, and the effect be so gradual as not to arrest attention; yet it is a violation of the physical laws, and, sooner or later, we pay the penalty in disease and suffering.

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979. Why is it incumbent on every person to learn the laws of health? 980. Give a law of the muscles. 981. In preserving the health, is it necessary to give attention to the food which is eaten? Why? 982. What beside food is essential to the full enjoyment of health? What is said of the impure air of unventilated rooms? 983. What should be observed in regard to sleep?

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983. The body also requires sleep; and if it is not taken at the right time, or with regularity, we do not feel full refreshment from "tired nature's sweet restorer." Let youth be taught that "early to bed and early to rise" gives him health and its attendant blessings. The brain, like other organs of the body, should be called into action at proper times.

984. From the extent of the surface of the skin, and the close sympathy that exists between it and those organs whose office is, to remove the waste particles of matter from the body, it therefore becomes very important in the preservation of the health, that the functions of this membrane be properly maintained.

985. The function of the circulatory and secretory organs, together with the operations of absorption and nutrition, should be steadily maintained, as vitality and the generation of animal heat are intimately connected with these processes. In the proper performance of these functions, very much depends on the observance of the laws of the muscular, digestive respiratory, dermoid, and nervous apparatuses.

REMOVAL OF DISEASE.

986. It is seldom that a physician is called in the first stages of disease. At this important period, the treatment adopted should be proper and judicious, or the sufferings of the patient are increased, and life, to a greater or less degree, is jeopardized. Hence the utility of knowing what should be done, and what should not be done, in order that the health may be rapidly regained.

987. In all instances of acute disease, it is proper to rest, not only the body, but the mind. To effect this, the patient should cease from physical exertion, and also withdraw his thoughts from study and business operations. This should be done, even if the person is but slightly indisposed.

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984. Why should the functions of the skin be properly maintained? 985. Show the necessity of maintaining properly other functions of the system. 986. What is important in the first stages of disease? 987. What is proper in all instances of acute disease? How can it be effected?

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988. Select a room for a sick person that is exposed to as little external noise as possible, as impressions made on the organ of hearing greatly influence the nervous system. Likewise select a spacious, well-ventilated apartment, that has no superfluous furniture. The practice of placing a sick person in a small, ill-arranged sleeping-room, when a more spacious room can be used, is poor economy, not to say unkind.

989. Care is necessary in regulating the light of a sick-room. While a strong light would produce an increased action of the vessels of the brain, a moderate light would be an appropriate stimulus to this organ. It is seldom or never necessary to exclude all light from the sick-chamber.

990. A sick person, whether a child or an adult, should not be disturbed by visitors, even if their calls are short. The excitement of meeting them is followed by a depression of the nervous system. The more dangerous and apparently nearer death the sick person is, the more rigorous should be the observance of this suggestion. Nor should the sick-room be opened to privileged classes; for the excitement caused by a visit from relations and the virtuous, will do as much injury to the sick, as that produced by strangers and the vicious.

991. The custom of visiting and conversing with sick friends during the intervals of daily labor, and particularly on Sunday, is a great evil. No person will thus intrude herself in the sick-chamber who cares more for the welfare of the suffering friend than for the gratification of a sympathetic curiosity. Inquiries can be made of the family respecting the sick, and complimentary or necessary messages can be communicated through the nurse.

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988. What rooms should be selected for the sick? Why? 989. What is said in reference to the quantity of light admitted into a sick-room? 990. What effect have calls on the sick? 991. What is said of the custom of calling and conversing with the sick during the intervals of daily labor?

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Illustration. While attending a Miss B., of N. H., sick of fever, I pronounced her better, withdrew medicine, directed a simple, low diet, and the exclusion of all visitors. In the evening I was sent for to attend her. There was a violent relapse into the disease, which continued to increase in severity until the fourth day, when death terminated her sufferings. I learned that, soon after I gave directions that no visitors be admitted into her room, several particular friends were permitted to enter the chamber and talk with the sick girl. Their conversation produced a severe headache; and, to use the language of the patient, "it seemed as if their talk would kill me;" and it did kill her.

992. No solid food should be taken in the first stages of disease, even if the affection is slight. The thirst can be allayed by drinking cold water, barley-water, and other preparations of an unstimulating character. It is wrong to tempt the appetite of a person who is indisposed. The cessation of a desire for food, is the warning of nature, that the system is in such a state that it cannot be digested.

993. When a patient is recovering from illness, the food should be simple, and in quantities not so great as to oppress the stomach. It should also be given with regularity. "Eat little and often," with no regard to regularity, is a pernicious practice.

994. When a physician attends a sick person, he should have the special management of the food, particularly after the medicine has been withdrawn and the patient is convalescent. The prevailing idea that every person may safely advise relative to food, or that the appetite of the convalescing person is a competent guide, is dangerous; and cannot be too much censured.

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Give an illustration. 992. What suggestion relative to food in the first stages of disease? How can the thirst be allayed? 993. When the patient is convalescent, how should the food be given? What is said of the practice of eating "little and often"? 994. Who should have the special management of food when medicine is withdrawn? What idea prevails in the community?

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Illustration. In 1832, I attended a Miss M., sick of fever. After an illness of a few days, the fever abated, and I directed a simple, unstimulating diet. Business called me from the town two days. During my absence, a sympathizing, officious matron called; found her weak, but improving; and told her she needed food to strengthen her; and that "it would now do her good." Accordingly, eggs and a piece of beefsteak were prepared, and given to the convalescent girl. She ate heartily, and the result was a relapse into a fever more violent than the first attack.

995. It is very important in disease that the skin be kept clean. A free action of the vessels of this part of the body exerts a great influence in removing disease from the internal organs, as well as keeping them in health. If the twenty or thirty ounces of waste, hurtful matter, that passes through the "pores" of the skin in twenty-four hours, are not removed by frequent bathing and dry rubbing, it deranges the action of the vessels that separate this waste matter from the blood, and thus increases the disease of the internal organs.

Illustration. Mrs. M. R., of N., Mass., was afflicted with disease of the lungs and cough. This was accompanied with a dry, inactive condition of the skin. As medicine had no salutary effect in relieving her cough, she was induced by the advice of the clergyman of the parish to enter upon a systematic course of bathing twice every day. Soon the skin became soft, its proper functions were restored, the disease of the lungs yielded, and the cough disappeared.

996. Every sick person should breathe pure air. The purer the blood that courses through the body, the greater the energy of the system to remove disease. The confined vitiated air of the sick-chamber, not unfrequently prolongs disease; and in many instances, the affection is not only aggravated, but, even rendered fatal, by its injurious influences.

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Give an illustration of the evil effects attending such an idea. 995. Does the skin exert a great influence in removing disease from the internal organs, as well as in keeping them in health? Give an illustration 996. Why should every sick person, particularly, breathe pure air?

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Illustrations. 1st. In 1833, I was called, in consultation with another physician, to Mr. H., who was much debilitated, and delirious. For several successive days he had not slept. His room was kept very warm and close, for fear he would "take cold." The only change that I made in the treatment, was to open the door and window, at a distance from the bed. In a short time, the delirium ceased, and he fell into a quiet slumber. From this time he rapidly recovered, and the delirium was probably the result of breathing impure air.

2d. Formerly, every precaution was used to prevent persons sick of the small-pox from breathing fresh air. When Mrs. Ramsay had this disease in Charleston, S.C., her friends, supposing that life was extinct, caused her body to be removed from the house to an open shed. The pure air revived the vital spark. The result probably would have been different, had she been kept a few hours longer in the vitiated air.

997. The influence of habit should not be disregarded in the removal of disease. If food or drink is to be administered, however small in quantity or simple its quality, it should be given at or about the time when the ordinary meals were taken in health.

998. Again, the usual time when the patient was in the habit of retiring for sleep should be observed, and all preparation necessary for the sick-room during the night should be made previous to this hour. Efforts should also be made to evacuate the waste matter of the digestive and urinary organs at the period which habit has formed in health. This is not only a remedial agent in disease, but often precludes the necessity of laxative or drastic cathartics.

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Are not diseases prolonged, and even rendered fatal, from breathing the impure, vitiated air of the sick-chamber? Give illustration 1st. Give illustration 2d. 997. What is said respecting the influence of habit in removing disease?

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999. MEDICINE is sometimes necessary to assist the natural powers of the system to remove disease; but it is only an assistant. While emetics are occasionally useful in removing food and other articles from the stomach that would cause disease if suffered to remain, and cathartics are valuable, in some instances, to relieve the alimentary canal of irritating residuum, yet the frequent administration of either will cause serious disease.

1000. Although medicine is useful in some instances, yet, in a great proportion of the cases of disease, including fevers and inflammations of all kinds, attention to the laws of health will tend to relieve the system from disease; more certainly and speedily, and with less danger, than when medicines are administered.

1001. Thomas Jefferson, in writing to Dr. Wistar, of Philadelphia, said, "I would have the physician learn the limit of his art." I would say, Have the matrons, and those who are continually advising "herb teas," and other "cure-alls," for any complaint, labelled with some popular name, learn the limits of their duty, namely, attention to the laws of health. The rule of every family, and each individual, should be, to touch not, taste not of medicine of any kind, except when directed by a well-educated and honest physician, (sudden disease from accidents excepted.)

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999. What is said of the use of medicine? 1000. Of its use in fevers and many other cases of disease? 1001. What remark by Thomas Jefferson to Dr. Wistar? What should matrons learn? What should be the rule of every person in regard to taking medicine? What exception?

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CHAPTER XLIX.

DIRECTIONS FOR NURSES.

1002. The nurse requires knowledge and practice to enable her to discharge aright her duty to the patient, as much as the physician and surgeon do to perform what is incumbent on them. Woman, from her constitution and habits, is the natural nurse of the sick; and, in general, no small portion of her time is spent in ministering at the couch of disease and suffering.

1003. As the young and vigorous, as well as the aged and the infirm, are liable to be laid upon the bed of sickness, by an epidemic, or imprudent exposure, or by some accident, it is therefore necessary that the girl, as well as the matron, may know how she can render services in an efficient and proper manner. No girl should consider her education complete who is not acquainted with the principles of the duties of a general nurse and a temporary watcher.

1004. It is to be regretted, that while we have medical schools and colleges to educate physicians, there is no institution to educate nurses in their equally responsible station. In the absence of such institutions, the defect can be remedied, to some extent, by teaching every girl hygiene, or the laws of health. To make such knowledge more available and complete, attention is invited to the following suggestions relative to the practical duties of a nurse.

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1002. Does the nurse require knowledge and practice in her employment, as well as the physician? Who is the natural nurse of the sick? 1003. What, then, is incumbent on every girl? 1004. Should there be schools to educate nurses, as well as physicians and surgeons?

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1005. BATHING. The nurse, before commencing to bathe the patient, should provide herself with water, two towels, a sponge, a piece of soft flannel, and a sheet. The temperature of the room should also be observed.

1006. When the patient is feeble, use tepid or warm water. Cold water should only be used when the system has vigor enough to produce reaction upon the skin. This is shown by the increased redness of the skin, and a feeling of warmth and comfort, after a proper amount of friction. Before using the sponge to bathe, a sheet, or fold of cloth, should be spread smoothly over the bed, and under the patient, to prevent the bed-linen on which the patient lies from becoming damp or wet.

1007. Apply the wet sponge to one part of the body at a time; as the arm, for instance. By doing so, the liability of contracting chills is diminished. Take a dry, soft towel, wipe the bathed part, and follow this by vigorous rubbing with a crash towel, or, what is better, a mitten made of this material; then use briskly a piece of soft flannel, to remove all moisture that may exist on the skin, and particularly between the fingers and the flections of the joints. In this manner bathe the entire body.

1008. The sick should be thoroughly bathed, at least twice in twenty-four hours. Particular attention should be given to the parts between the fingers and toes, and about the flections of the joints, as the accumulation of the excretions is most abundant on these parts. In bathing, these portions of the system are very generally neglected. The best time for bathing, is when the patient feels most vigorous, and freest from exhaustion. The practice of daubing the face and hands with a towel dipped in hot rum, camphor, and vinegar, does not remove the impurities, but causes the skin soon to feel dry, hard, and uncomfortable.

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1005. What should a nurse provide herself with, before bathing a patient? 1006. When should cold water be used? 1007. How should the bathing then be performed, so that the patient may not contract a cold? 1008. How often should a sick person be bathed? What is said of daubing the face and hands merely with a wet cloth?

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1009. FOOD. It is the duty of every woman to know how to make the simple preparations adapted to a low diet, in the most wholesome and the most palatable way. Water-gruel,[24] which is the simplest of all preparations, is frequently so ill-made as to cause the patient to loathe it. Always prepare the food for the sick, in the neatest and most careful manner.

[24] Directions for making the simple preparations for the sick are found in almost every cook-book.

1010. When the physician enjoins abstinence from food, the nurse should strictly obey the injunction. She should be as particular to know the physician's directions about diet, as in knowing how and when to give the prescribed medicines, and obey them as implicitly.

1011. When a patient is convalescent, the desire for food is generally strong, and it often requires firmness and patience, together with great care, on the part of the nurse, that the food is prepared suitably, and given at proper times The physician should direct how frequently it should be taken.

1012. PURE AIR. It is the duty of the nurse to see that not only the room is well ventilated in the morning, but that fresh air is constantly admitted during the day. Great care must be taken, however, that the patient does not feel the current.

1013. Bed-linen, as well as that of the body, should be aired every day, and oftener changed in sickness than in health. All clothing, when changed, should be well dried, and warmed by a fire previous to its being put on the patient or the bed.

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1009. Should every woman know how to make the simple preparations adapted to a low diet? 1010. Should the nurse strictly obey the injunctions of the physician relative to food? 1011. What period of a person's illness requires the most care in regard to the food? 1012. Give another duty of the nurse. 1013. What directions respecting the bed-linen of the patient? What is necessary when there is a change of clothing?

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1014. TEMPERATURE. The warmth of the chamber should be carefully watched by the nurse. The feelings of the patient or nurse are not to be relied on as an index of the temperature of the room. There should be a well-adjusted thermometer in every sick-room. This should be frequently consulted by the nurse.

1015. The temperature of the sick-chamber should be moderate. If it is so cold as to cause a chill, the disease will be aggravated. If, on the other hand, it is too warm, the patient is enfeebled and rendered more susceptible to cold on leaving the sick-chamber. The Latin maxim, "In medio tutissimus ibis," (in medium there is most safety,) should be regarded in the rooms of the sick.

1016. QUIET. The room of the patient should be kept free from noise. The community should be guided by this rule, that no more persons remain in the room of the sick, than the welfare of the patient demands. It is the duty of the physician to direct when visitors can be admitted or excluded from the sick-room, and the nurse should see that these directions are enforced.

1017. The movements of the attendants should be gentle and noiseless. Shutting doors violently, creaking hinges, and all unnecessary noise, should be avoided. Most persons refrain from loud talking in the sick chamber, but are not equally careful to abstain from whispering, which is often more trying than a common tone.

1018. It is the duty of the nurse to ascertain the habits of the patient as respects the period for eating and sleep, when in health, that she may prepare the food and arrange the sick-room in accordance with the practice of the patient. If the person who is sick is ignorant of the necessity of the removal of the waste products from the system the nurse should invite attention to these functions at such periods as are in accordance with the previous habits of the patient.

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1014. Why should there be a well-adjusted thermometer in every sick-chamber? 1015. What is said of the temperature of the sick-chamber? 1016. Why should the sick-room be kept quiet? 1017. What is said of noise in the sick-chamber? Of whispering? 1018. Should the habits of the patient be regarded in reference to the period for eating and sleep?

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1019. The deportment and remarks of the nurse to the patient should be tranquil and encouraging. The illness of a friend, or persons who have recently died, should not be alluded to in the sick-room. No doubts or fears of the patient's recovery, either by a look or by a word, should be communicated by the nurse in the chamber of the sick. When such information is necessary to be communicated, it is the duty of the physician to impart it to the sick person.

1020. The nurse should not confine herself to the sick-room more than six hours at a time. She should eat her food regularly, sleep at regular periods, and take exercise daily in the open air. To do this, let her quietly leave the room when the patient is sleeping. A watcher, or temporary nurse, may supply her place. There is but little danger of contracting disease, if the nurse attends to the simple laws of health, and remains not more than six hours at a time in the sick-room.

DIRECTIONS FOR WATCHERS.

1021. These necessary assistants, like the nurse, should have knowledge and practice. They should ever be cheerful, kind, firm, and attentive in the presence of the patient.

1022. A simple, nutritious supper should be eaten before entering the sick-room; and it is well, during the night, to take some plain food.

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1019. What should be the deportment of the nurse toward the patient? Should doubts and fears of the patient's recovery be communicated in the sick-room? When necessary to impart such intelligence, on whom does it depend? 1020. How long should a nurse remain in the sick-chamber at a time? 1021. What qualifications are necessary in a watcher? 1022. What directions in regard to the food of the watcher?

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1023. When watching in cold weather, a person should be warmly dressed, and furnished with an extra garment, as a cloak or shawl, because the system becomes exhausted toward morning, and less heat is generated in the body.

1024. Light-colored clothing should be worn by those who have care of the sick, in preference to dark-colored apparel; particularly if the disease is of a contagious character. Experiments have shown, that black and other dark colors will absorb more readily the subtile effluvia that emanate from sick persons, than white or light colors.

1025. Whatever may be wanted during the night, should be brought into the sick-chamber, or the adjoining room, before the family retires for sleep, in order that the slumbers of the patient be not disturbed by haste, or searching for needed articles.

1026. The same general directions should be observed by watchers, as are given to the nurse; nor should the watcher deem it necessary to make herself acceptable to the patient by exhausting conversation.

1027. It can hardly be expected that the farmer, who has been laboring hard in the field, or the mechanic, who has toiled during the day, is qualified to render all those little attentions that a sick person requires. Hence, would it not be more benevolent and economical to employ and pay watchers, who are qualified by knowledge and training, to perform this duty in a faithful manner, while the kindness and sympathy of friends may be practically manifested by assisting to defray the expenses of these qualified and useful assistants?

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1023. When watching in cold weather, what precaution is necessary? 1024. What is said relative to the color of the clothing worn in the sick-room? 1025. What suggestions to watchers relative to the arrangement of the sick-chamber? 1026. What should watchers observe? 1027. What is said of employing those persons to watch who labor hard during the day?

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APPENDIX.

POISONS AND THEIR ANTIDOTES

1028. POISONING, either from accident or design, is of such frequency and danger, that it is of the greatest importance that every person should know the proper mode of procedure in such cases, in order to render immediate assistance when within his power.

1029. Poisons are divided into two classes—mineral (which include the acids) and vegetable.

1030. The first thing, usually, to be done, when it is ascertained that a poison has been swallowed, is to evacuate the stomach, unless vomiting takes place spontaneously. Emetics of the sulphate of zinc, (white vitriol,) or ipecacuanha, (ipecac,) or ground mustard seed, should be given.

1031. When vomiting has commenced, it should be aided by large and frequent draughts of the following drinks: flaxseed tea, gum-water, slippery-elm tea, barley water, sugar and water, or any thing of a mucilaginous or diluent character.

MINERAL POISONS.

1032. AMMONIA.—The water of ammonia, if taken in an over-dose, and in an undiluted state, acts as a violent corrosive poison.

1033. The best and most effectual antidote is vinegar. It should be administered in water, without delay. It neutralizes the ammonia, and renders it inactive. Emetics should not be given.

1034. ANTIMONY.—The wine of antimony and tartar emetic, if taken in over-doses, cause distressing vomiting. In addition to the diluent, mucilaginous drinks, give a tea-spoonful of the sirup of poppies, paregoric, or twenty drops of laudanum, every twenty minutes, until five or six doses have been taken, or the vomiting ceases.

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1025. Is it useful to know the antidotes or remedies for poison? 1029. Into how many classes are poisons divided? 1030. What is the first thing to be done when it is ascertained that poison has been swallowed? 1031. What should be taken after the vomiting has commenced? 1032. What effect has an over-dose of ammonia? 1033. The antidote? Should an emetic be given for this poison? 1034. What effect has an over-dose of the wine of antimony or tartar emetic?

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1035. The antidotes are nutgalls and oak bark, which may be administered in infusion, or by steeping in water.

1036. ARSENIC.—When this has been taken, administer an emetic of ipecac, speedily, in mucilaginous teas, and use the stomach-pump as soon as possible.

1037. The antidote is the hydrated peroxide of iron. It should be kept constantly on hand at the apothecaries' shops. It may be given in any quantity, without injurious results.

1038. COPPER.—The most common cause of poisoning from this metal, is through the careless use of cooking utensils made of it, on which the acetate of copper (verdigris) has been allowed to form. When this has been taken, immediately induce vomiting, give mucilaginous drinks, or the white of eggs, diffused in water.

1039. The antidote is the carbonate of soda, which should be administered without delay.

1040. LEAD.—The acetate (sugar) of lead is the preparation of this metal, which is liable to be taken accidentally, in poisonous doses. Induce immediate vomiting, by emetics of ground mustard seed, sulphate of zinc, and diluent drinks.

1041. The antidote is diluted sulphuric acid. When this acid is not to be obtained, either the sulphate of magnesia, (epsom salts,) or the sulphate of soda, (glauber's salts,) will answer every purpose.

1042. MERCURY.—The preparation of this mineral by which poisoning is commonly produced, is corrosive sublimate. The mode of treatment to be pursued when this poison has been swallowed, is as follows: The whites of a dozen eggs should be beaten in two quarts of cold water, and a tumbler-full given every two minutes, to induce vomiting. When the whites of eggs are not to be obtained, soap and water should be mixed with wheat flour, and given in copious draughts, and the stomach-pump introduced as soon as possible. Emetics or irritating substances should not be given.

1043. NITRE—Saltpetre.—This, in over-doses, produces violent poisonous symptoms. Vomiting should be immediately induced by large doses of mucilaginous, diluent drinks; but emetics which irritate the stomach should not be given.

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1035. What is the antidote? 1036. What should immediately be done when arsenic is swallowed? 1037. What is the antidote? Can any quantity of this preparation of iron be given without injurious results? 1038. What should be given when verdigris has been taken into the stomach? 1039. What is the antidote? 1040. What should immediately be given when sugar of lead is taken? 1041. What is the antidote? 1042. Give the treatment when corrosive sublimate has been swallowed. 1043. What effect has an over-dose of saltpetre? What treatment should be adopted?

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1044. ZINC.—Poisoning is sometimes caused by the sulphate of zinc, (white vitriol.) When this takes place, vomiting should be induced, and aided by large draughts of mucilaginous and diluent drinks. Use the stomach-pump as soon as possible.

1045. The antidote is the carbonate, or super-carbonate of soda.

1046. NITRIC, (aqua fortis,) MURIATIC, (MARINE ACID,) OR SULPHURIC (OIL OF VITRIOL,) ACIDS, may be taken by accident, and produce poisonous effects.

1047. The antidote is calcined magnesia, which should be freely administered, to neutralize the acid and induce vomiting. When magnesia cannot be obtained, the carbonate of potash (salaeratus) may be given. Chalk, powdered and given in solution, or strong soap suds, will answer a good purpose, when the other articles are not at hand. It is of very great importance that something be given speedily, to neutralize the acid. One of the substances before mentioned should be taken freely, in diluent and mucilaginous drinks, as gum-water, milk, flaxseed, or slippery-elm tea. Emetics ought to be avoided.

1048. OXALIC ACID.—This acid resembles the sulphate of magnesia, (epsom salts,) which renders it liable to be taken, by mistake, in poisonous doses. Many accidents have occurred from this circumstance. They can easily be distinguished by tasting a small quantity. Epsom salts, when applied to the tongue, have a very bitter taste, while oxalic acid is intensely sour.

1049. The antidote is magnesia, between which and the acid a chemical action takes place, producing the oxalate of magnesia, which is inert. When magnesia is not at hand, chalk, lime, or carbonate of potash, (salaeratus,) will answer as a substitute. Give the antidote in some of the mucilaginous drinks before mentioned. No time should be lost in introducing the stomach-pump as soon as a surgeon can be obtained.

1050. LEY.—The ley obtained by the leaching of ashes may be taken by a child accidentally. The antidote is vinegar, or oil of any kind. The vinegar neutralizes the alkali by uniting with it, forming the acetate of potash. The oil unites with the alkali, and forms soap, which is less caustic than the ley. Give, at the same time, large draughts of mucilaginous drinks, as flaxseed tea, &c.

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1044. What is the antidote for white vitriol? 1047. What is the antidote for aqua fortis and oil of vitriol? Should emetics be avoided? 1048. How can oxalic acid be distinguished from epsom salts? 1049. What is the antidote for an over-dose of oxalic acid? When magnesia cannot be obtained, what will answer as a substitute? 1050. What is the antidote when ley is swallowed?

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VEGETABLE POISONS.

1051. The vegetable poisons are quite as numerous, and many of them equally as virulent, as any in the mineral kingdom. We shall describe the most common, and which, therefore, are most liable to be taken.

1052. OPIUM.—This is the article most frequently resorted to by those wishing to commit suicide, and, being used as a common medicine, is easily obtained. From this cause, also, mistakes are very liable to be made, and accidents result from it. Two of its preparations, laudanum and paregoric, are frequently mistaken for each other; the former being given when the latter is intended.

1053. Morphia, in solution, or morphine, as it is more commonly called by the public, is a preparation of the drug under consideration, with which many cases of poisoning are produced. It is the active narcotic principle of the opium; and one grain is equal to six of this drug in its usual form.

1054. When an over-dose of opium, or any of its preparations, has been swallowed, the stomach should be evacuated as speedily as possible. To effect this, a teaspoonful of ground mustard seed, or as much tartar emetic as can be held on a five cent piece, or as much ipecacuanha as can be held on a twenty-five cent piece, should be mixed in a tumbler of warm water, and one half given at once, and the remainder in twenty minutes, if the first has not, in the mean time, operated. In the interval, copious draughts of warm water, or warm sugar and water, should be drank.

1055. The use of the stomach-pump, in these cases, is of the greatest importance, and should be resorted to without delay. After most of the poison has been evacuated from the stomach, a strong infusion of coffee ought to be given; or some one of the vegetable acids, such as vinegar, or lemon-juice, should be administered.

1056. The patient should be kept in motion, and salutary effects will often be produced by dashing a bucket of cold water on the head. Artificial respiration ought to be established, and kept up for some time. If the extremities are cold, apply warmth and friction to them. After the poison has been evacuated from the stomach, stimulants, as warm wine and water, or warm brandy and water, should be given, to keep up and sustain vital action.

1057. STRAMONIUM—Thorn-Apple.—This is one of the most active narcotic poisons, and, when taken in over-doses, has, in numerous instances, caused death.

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1051. Are vegetable poisons as numerous and as virulent in their effects as mineral? 1052. What is said of opium and its preparations? 1054, 1055, 1056. What treatment should be adopted when an over-dose of opium or any of its preparations is taken? 1057. What is said of stramonium?

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1058. HYOSCIAMUS—Henbane.—This article, which is used as a medicine, if taken in improper doses, acts as a virulent irritating and narcotic poison.

1059. The treatment for the two above-mentioned articles is similar to that of poisoning from over-doses of opium.

1060. CONIUM—Hemlock.—Hemlock, improperly called, by many, cicuta, when taken in an over-dose, acts as a narcotic poison. It was by this narcotic that the Athenians used to destroy the lives of individuals condemned to death by their laws. Socrates is said to have been put to death by this poison. When swallowed in over-doses, the treatment is similar to that of opium, stramonium, and henbane, when over-doses are taken.

1061. BELLADONNA—Deadly Nightshade.—CAMPHOR. ACONITE—Monkshood, Wolfsbane. BRYONIA—Bryony. DIGITALIS—Foxglove. DULCAMARA—Bittersweet. GAMBOGE. LOBELIA—Indian Tobacco. SANGUINARIA—Bloodroot. OIL OF SAVIN. SPIGELIA—Pinkroot. STRYCHNINE—Nux vomica. TOBACCO.—All of these, when taken in over-doses, are poisons of greater or less activity. The treatment of poisoning, by the use of any of these articles, is similar to that pursued in over-doses of opium. (See OPIUM, page 442.)

1062. In all cases of poisoning, call a physician as soon as possible.

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1058. Of henbane? 1059. What should be the treatment when an over-dose of stramonium or henbane is taken? 1060. What name is sometimes improperly given to conium, or hemlock? How was this narcotic poison used by the Athenians? How are the effects of an over-dose counteracted? 1061. What is the treatment when an over-dose of deadly nightshade, monkshood, foxglove, bittersweet, gamboge, lobelia, bloodroot, tobacco, &c., is taken? 1062. Should a physician be called in all cases when poison is swallowed?

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A.

The essential parts of every secretory apparatus are a simple membrane, apparently textureless, named the primary, or basement membrane, certain cells and blood-vessels. The serous and mucous membrane are examples.

B.

The division and description of the different membranes and tissues are not well defined and settled by anatomical writers. This is not a material defect, as a clear description of the different parts of the system can be given by adopting the arrangement of almost any writer.

C.

FAT is one of the non-nitrogenous substances. It forms the essential part of the adipose tissue. Chemical analysis shows that all fatty substances are compounds of carbon, hydrogen, and oxygen. They are lighter than water, generally fluid at the natural temperature of the body, and burn with a bright flame, forming water and carbonic acid.

CASEINE is abundantly found in milk. When dried, it constitutes cheese. Alcohol, acids, and the stomach of any of the mammalia coagulate it; and it is also soluble in water. It is found in the blood, bile, saliva, and the lens of the eye.

CHONDRINE is a variety of gelatin. It is obtained from cartilage. It is soluble in warm water, but solidifies on cooling.

LACTIC ACID is common to all the solids and fluids of the system. It is found united with potash, soda, lime, or magnesia.

D.

The word duodenum is derived from the Latin, signifying "twelve," since the intestine, of which this is the name, is usually about twelve fingers' breadth in length. The jejunum is also from the Latin jejunum, empty, since it is usually found in that condition after death, as the food seems to pass rapidly through this part of the intestine. The term ileum is from the Greek, signifying "to twist," since it always appears in a contorted condition. The name caecum is derived from the fact of its being a blind or short sack, perforated by the extremity of the ileum. The name of the next division of the intestine—colon—is from the Greek, "to prohibit," as the contents of the alimentary canal pass slowly through this portion. The rectum is named from the straight direction that it assumes in the latter part of its course.

E.

The food is forced through the alimentary canal by contractions of its muscular coat, produced by the nervous filaments of the sympathetic system, not being at all dependent on the cerebro-spinal centre. This is called the peristaltic, or vermicular motion. The great length of intestine in all animals, and especially in the herbivorous ones, is owing to the necessity of exposing the food to a large number of the lacteals, that the nourishment may all be taken from it.

F.

The different processes through which the food passes before assimilation are of considerable interest. The mastication and mixture of the saliva with the food are purely of a mechanical nature. When any solid or fluid substance is placed upon the tongue, or in contact with the inner surface of the cheeks, by an involuntary act, the salivary glands are stimulated to activity, and commence pouring the saliva into the mouth through the salivary ducts. As soon as mastication commences, the contraction of the masseter and other muscles employed in mastication stimulates the salivary glands to increased action, and a still greater quantity of saliva is secreted and forced upon the food, which is constantly being ground to a finer condition, until it is sufficiently reduced for deglutition.

Whether the salivary fluid acts any other part than simply that of a demulcent to assist the gastric juice in still further dissolving the food, is yet a matter of some doubt, although it is found that no other liquid will equally well subserve the process of digestion and promote health.

After the food is in the condition ready to be swallowed, by an apparently involuntary motion, it is placed upon the back of the tongue, which carries it backwards to the top of the pharynx, where the constrictions of the pharynx, aided by the muscles of the tongue and floor of the mouth, with a sudden and violent movement thrust it beyond the epiglottis, in order to allow the least necessary time to the closure of the glottis, after which, by the compression of the oesophagus, it is forced into the stomach.

Here it is that the true business of digestion commences. For as soon as any substance except water enters the stomach, this organ, with involuntary movements, that seem almost like instinct, commences the secretion of the gastric juice, and by long-continued contractions of its muscular coat, succeeds in effecting a most perfect mixture of the food with this juice, by which the contents of the stomach are reduced to the softest pulp.

The gastric juice, in its pure state, is a colorless, transparent fluid; "inodorous, a little saltish, and perceptibly acid. It possesses the property of coagulating albumen, and separating the whey of milk from its curd, and afterwards completely dissolving the curd. Its taste, when applied to the tongue, is similar to that of mucilaginous water, slightly acidulated with muriatic acid." The organs of its secretion are an immense number of tubes or glands, of a diameter varying from one five hundredth to one three hundredth of an inch, situated in the mucous coat of the stomach, and receiving their blood from the gastric arteries. A chemical analysis shows it to consist of water, mucilage, and the several free acids—muriatic, acetic, lactic, and butyric, together with a peculiar organic matter called pepsin, which acts after the manner of ferments between the temperature of 50 deg. and 104 deg. F.

The true process of digestion is probably owing to the action of pepsin and the acids, especially if the presence of the chloro-hydric or muriatic be admitted; since we know, by experiments out of the body, that chlorine, one of its elements, is a powerful solvent of all organic substances.

The antiseptic properties of the gastric juice, as discovered by experiments made on Alexis St. Martin, doubtless have much influence on digestion, although their true uses are probably not yet known.

As soon as the food is reduced to a state of fluidity, the pyloric orifice of the stomach is unclosed, and it is thrust onwards through the alimentary canal, receiving in the duodenum the secretions of the liver and pancreas, after which it yields to the lacteals its nutrient portion, and the residuum is expelled from the body.

There have been many hypotheses in regard to the nature of the digestive process. Some have supposed that digestion is a mere mechanical process, produced by the motion of the walls of the stomach; while others, in later times, have considered it as under the influence of a spirit separate from the individual, who took up his residence in the stomach and regulated the whole affair; while others still would make it out to be a chemical operation, and thus constitute the stomach a sort of laboratory. But to all these ridiculous hypotheses Sir John Hunter has applied the following playful language: "Some will have it that the stomach is a mill; others that it is a fermenting vat; and others that it is a stewpan; but in my view of the matter, it is neither a mill, a fermenting vat, nor a stewpan, but a stomach, a stomach!"