Symptoms.—The animal is observed to limp. On examination of the foot we discover heat and swelling above the hoof and of the soft parts between the claws which frequently spreads the claws apart to a considerable extent, or the inflammation may have advanced to softening and sloughing of the interdigital membrane. If the disease is neglected at this stage, deep abscesses may form and the pus burrow under the horny wall, or the joint within the hoof may become inflamed and the articular attachments destroyed, in which case the treatment will be difficult and recovery will be very tedious.

Treatment.—In the earlier stages of the disease, before pus burrows beneath the horn, a thorough cleansing and an application of a carbolic-acid solution—1 ounce to a pint of water—clean stabling, and laxative food will usually remedy the evil. Compound solution of cresol is an excellent remedy at this stage. It should be applied, in its pure or undiluted state, to the suppurating and putrefying tissue between the claws. It is best applied by means of a cotton swab on a thin stick. Care must be taken to keep it from contact with the skin about the coronary band or heels. If deep sloughing has taken place the carbolic solution should be used, and a wad of oakum or cotton smeared with pine tar should be secured firmly in the cleft. This can be done by taking a strip of strong cloth, 2 inches wide, passing the middle between the claws, then tying the ends after winding them in opposite directions above the hoof. Sometimes warm poulticing with flaxseed meal or bran is necessary to relieve excessive fever and pain. If the pus burrows under the horn, its channel must be followed by paring away the horn until the bottom is reached. The aftertreatment is the same as that already recommended. If the joint becomes diseased an amputation of that toe is the quickest and surest method to relieve the suffering of the animal, and offers the best chance for an early recovery.

ULCERATION OF THE HEEL.

Occasionally we find ulcers at the junction of the hair with the hoof at the heel, which present an elevated, raw, or ragged surface, and cause considerable lameness. This is generally caused by a bruise of the fibrous cushion of the back part of the foot. Subsequent sloughing or necrosis may occur, or pus may form deep within the wall and gain an exit at the margin of the heel. Sometimes, from no visible cause, large pieces of skin slough from the heel and pastern. This condition is caused by an infection with certain microorganisms (streptococci, necrosis bacilli) and may be contagious.

Treatment.—If there is a deep opening, inject carbolic solution once a day until it closes. If the ulcer is only superficial, wash with carbolic solution and apply a mixture of equal parts of blue vitriol and alum in dry powder.

FISSURE OF THE WALL (SPLIT HOOF).

This is rarely seen among cattle. It may occur in weak walls, in heavily bodied cattle, caused by stepping on an uneven surface, especially when the point of the toe is grown out long. One may find the point of the toe broken and the wall split almost up to the hair.

Treatment.—The divided sections may be brought into approximation and held in place by drilling a small hole from one side into and through the other, commencing half an inch back of the fissure on each side; then drive a light horseshoe nail through the hole and clinch it. Pare the injured claw as short as it will bear.

INTERDIGITAL FIBROMA.

Hard, nodular, fibrous tumors sometimes grow in the cleft of the foot, and cause inconvenience, lameness, absorption, or ulceration of the contiguous parts.

Treatment.—They should be dissected out and the wound dressed with carbolic-acid lotion and pine tar once a day until healing is completed.

DEFORMITIES.

Deformities in the feet of cattle usually consist in overgrowth of horn, generally from want of wear in animals which are stabled. The hoof may turn inward, outward, or upward, and may give rise to lameness, inability to walk, foul foot, etc. Bulls which are continually stabled and dairy cows very frequently have misshapen feet from want of an occasional trimming, and this deformity may eventually lead to permanent injury.

Treatment.—Cut the superabundant growth of horn down with saw, knife, or rasp, until the foot assumes its natural form.

PRICKS AND WOUNDS.

If an animal suffers with a penetrating wound from prick of fork or nail, the orifice of the wound should be enlarged to permit a free discharge of pus; then the foot should be soaked in a cresol compound solution (3 per cent) in a tub, or a flaxseed poultice applied, changing it three times a day until the fever has abated. The foot should be kept bandaged and dressed with pine tar and oakum; the animal must also be kept on a clean floor until the wound is closed and all or nearly all lameness has disappeared.

If an animal is cut in the foot with barbed wire, piece of glass, or any other substance, the wound, after proper cleansing, should be dressed with carbolic-acid solution, 1 ounce of the acid to 20 of water. If any uneven edges of horn, skin, or lacerated flesh project, trim them off, and in all cases when it can be done a tarred bandage should be applied. This will serve to sustain the cut surfaces in their place, exclude dirt, and protect against flies, maggots, etc.

When the wound has extended into a joint, surgical treatment, which will require the services of an educated veterinarian, may be necessary.

Occasionally an animal gets caught by the foot in a crevice and sustains severe bruising, wrenching, or fracture of some part of the foot. In such cases cold-water packs to the injured member are of service until the fever and swelling disappear. Afterwards the animal should rest until the usefulness of the foot is restored. Sometimes such an accident, causing fracture, renders necessary plaster bandages or amputation.



DISEASES OF THE EYE AND ITS APPENDAGES.

By M. R. TRUMBOWER, D. V. S.

[Revised by Leonard Pearson, B. S., V. M. D.]

DESCRIPTION.

For the sake of gaining a clear comprehension of the diseases of the eye it becomes necessary to review the anatomy of this important organ. The essential organ of vision, or globe of the eye, will be first described, then its receptacle or orbital cavity, the muscles that move it, the protective membranes, or eyelids, the membrana nictitans, or accessory eyelids, and, lastly, the lacrimal apparatus.

The globe or ball of the eye is almost spherical in form. On closer inspection, however, it appears to be made up of two combined portions from spheres of different sizes. The posterior portion, forming about five-sixths of the ball, is a sphere of comparatively large size with a small segment cut off it in front, and at this point there is applied to it the anterior portion, which, being a segment of a smaller sphere, projects at the front of the ball with a greater convexity than the posterior portion.

The eyeball consists of concentrically arranged coats and of refracting media inclosed in them. The coats are three in number, namely, (1) an external protective tunic made up of the sclerotic and cornea; (2) a middle vascular and pigmentary tunic, the choroid; (3) an internal nervous layer, the retina. The sclerotic is the white, opaque part of the outer tunic, of which it forms about the posterior five-sixths, being coextensive with the larger sphere already mentioned. The cornea forms the remaining one-sixth of the outer tunic, being coextensive with the segment of the smaller sphere. It is distinguished from the sclerotic by being colorless and transparent. The choroid coat will be recognized as the black layer lying subjacent to the sclerotic. It does not line the cornea, but terminates behind the line of junction of that coat with the sclerotic by a thickened edge—the ciliary processes. At the line of junction of the sclerotic and cornea the iris passes across the interior of the eye. This (which may be viewed as a dependency of the choroid) is a muscular curtain perforated by an aperture termed the pupil. The retina will be recognized as a delicate, glassy layer, lining the greater part of the choroid.

The refracting media of the eye are three in number, namely (1) the aqueous humor, a watery fluid inclosed in a chamber behind the cornea; (2) the crystalline lens and its capsule, a transparent, soft solid of a biconvex form, and placed behind the iris; (3) the vitreous humor, a transparent material with a consistence like thin jelly, and occupying as much of the interior of the eye as is subjacent to the choroid.

The sclerotic is a strong, opaque, fibrous membrane, which, in a great measure, maintains the form of the eyeball and protects the more delicate structures within it. Its interior portion, which is covered by the ocular conjunctiva, is commonly known as the "white of the eye." In form it is bell-shaped, and the optic nerve pierces it behind like a handle, the perforation being a little to its inner side. In front, the rim of the bell becomes continuous with the cornea. The outer surface of the membrane receives the insertion of the muscles of the eyeball. The coat is thickest over the posterior part of the eyeball, and is thinnest a little behind its junction with the cornea.

The cornea is the anterior transparent portion of the outer coat of the eyeball. It may be viewed as a part of the sclerotic specially modified to permit the passage of light into the interior of the eye. Its outline is elliptical, nearly circular, and its greatest diameter is transverse. At its periphery it joins the sclerotic by continuity of tissue, and as the edge of the cornea is slightly beveled and has the fibrous sclerotic carried for a little distance forward on its outward surface, the cornea is generally said to be fitted into the sclerotic like a watch glass into its rim. The venous canal of Schlemm runs circularly around the eyeball at the line of junction of the sclerotic and cornea. The anterior surface of the cornea is exquisitely smooth, and is kept moist by the lacrimal secretions. Its posterior surface forms the anterior boundary of the chamber in which the aqueous humor is contained. The cornea is of uniform thickness and is of a dense, almost horny, consistence. Save a few capillary loops of blood vessels at its margin the cornea is without vessels. Its structure is comprised of five distinct layers.

The aqueous humor occupies a chamber which is bounded in front by the posterior surface of the cornea and behind by the capsule and suspensory ligament of the lens and by the ends of the ciliary processes. It is across this chamber that the iris extends. The aqueous humor is composed of water, with a small proportion of common salt in solution.

The iris is a muscular, pigmented curtain extending across the interior of the eye and having about its center an aperture termed the pupil. By variations in the size of this aperture the amount of light transmitted to the retina is regulated. It varies somewhat in color, but is most frequently of a yellowish-brown tint. Its anterior face is bathed by the aqueous humor. The greater part of the posterior surface is in contact with the capsule of the lens and glides on it during the movements of the curtain. The circumferential border is attached within the junction of the sclerotic cornea. The inner border circumscribes the pupil, which varies in outline according to its size. When much contracted the pupil is a very elongated ellipse, the long axis of which is in the line joining the nasal and temporal angles of the eyelids. It contains muscular tissue, which, by contracting or relaxing, lessens or dilates the pupillary opening.

The choroid coat is a bell-shaped, dark membrane which lines the sclerotic. Its outer surface has a shaggy appearance, caused by the tunica fusca, which unites the two coats. Between the two the ciliary vessels and nerves pass forward. Behind it is pierced by the optic nerve; in front it is continued as the ciliary processes, which form, as it were, the rim of the bell. The ciliary processes form a fringe around the slightly inverted rim of the choroid.

The retina is the most delicate of the coats of the eyeball. It is formed by the expansion of the optic nerve on the inner surface of the choroid, and, like that coat, it is bell-shaped. Its inner surface is molded on the vitreous humor. The nervous structures of the retina terminate at a wavy line, the ora serrata, behind the ciliary processes. Ten distinct layers are described as composing the thickness of the retina.

The lens is situated behind the pupil and is contained within a capsule of its own.

The capsule is a close-fitting, firm, transparent membrane. The anterior surface forms the posterior boundary of the cavity containing the aqueous humor, and the iris in its movement glides on it. The posterior surface is in contact with the vitreous humor.

The vitreous humor occupies four-fifths of the interior of the eyeball. It is globular in form, with a depression in front for the lodgment of the lens. It is colorless, transparent, and of a consistency like thin jelly. It is enveloped by a delicate capsule—the hyaloid membrane—which is connected in front with the suspensory ligament of the lens, and ends by joining the capsule behind the lens.

The orbital cavity, at the side of the head, is circumscribed by a bony margin; posteriorly, however, there are no bony walls, and the cavity is often confounded with the depression above and behind the orbit—the temporal fossa. A fibrous membrane completes this cavity and keeps it distinct from the temporal fossa. This membrane—the ocular sheath or periorbita—is attached posteriorly around the opening in the back part of the orbital cavity (the orbital hiatus) and anteriorly to its inner face; then it becomes prolonged beyond the margin to form the fibrous membrane of the eyelids. When complete the orbital cavity has the form of a regular hollow cone, open at its base and closed at the apex. The opening of this cone is directed forward, downward, and outward. Independently of the globe of the eye, this cavity lodges the muscles that move it, the membrana nictitans, and the lacrimal gland.

The muscles of the eye are seven in number—one retractor, four straight, and two oblique. The retractor oculi envelops the optic nerve between the brain and the ball of the eye and becomes attached upon the external face of the sclerotic tunic. When this muscle contracts, it draws the globe back into the orbit, away from the light. The superior, inferior, external, and internal recti or straight muscles are attached to the back part of the orbital sheath and spread forward in four bundles over the globe of the eye, where they are inserted by a fibrous expansion into the sclerotic at the margin of the cornea. When they act singly, they turn the globe either upward, downward, inward, or outward. The great oblique, by its action, pivots the eye inward and upward in the orbit. The small oblique turns the eye outward and downward.

The eyelids are two movable curtains, superior and inferior, which cover and protect the eye in front. They are attached to the circumference of the orbit and have a convex external face formed by the skin and a concave internal face molded on the anterior surface of the eye and are lined by the conjunctiva, which is reflected above and below on the eyeball. The border of each lid is slightly beveled on the inner side and shows the openings of the Meibomian glands. These glands secrete an unctuous fluid, which is thrown out on the border of the lids, the function of which is to facilitate their movements and enable them to retain the tears in the ocular cavity. The eyelid is composed of a fibrous inner membrane ending in a stiff arch near the border, a muscle to close the lid, another to open it, the skin externally, and the conjunctival mucous membrane internally. The border of each lid is covered and protected by long hairs to prevent floating particles of matter in the atmosphere from gaining entrance to the eye.

The membrana nictitans, which is also named the third eyelid, winking eyelid, haw, etc., is placed at the inner angle of the eye, whence it extends over the eyeball to relieve it from foreign bodies which may fall upon it. It has for its framework a fibro-cartilage, irregular in shape, thick, nearly prismatic at its base, and thin anteriorly where it is covered by the conjunctiva; behind, it is loosely attached to a fatty cushion.

The lacrimal gland is situated between the orbital process and the upper part of the eyeball. It secretes the tears destined to lubricate the anterior surface of the eye. This fluid escapes upon the organ at the outer angle of the lids and is carried between them and the eyeball toward the inner angle.

The caruncula lacrimalis is a small round body, frequently entirely or partially black, situated in the inner angle of the eye, and is designed to direct the tears toward the puncta lacrimalia.

The puncta lacrimalia are two little openings, situated one in each eyelid, a short distance from the inner corner, which admit the tears into the lacrimal ducts leading to the lacrimal canal, whence they are emptied into the nasal passages.

CONJUNCTIVITIS (SIMPLE OPHTHALMIA).

This is an inflammation of the conjunctival mucous membrane of the eyeball and lids; in severe cases the deeper coats of the eye are involved, seriously complicating the attack.

Causes.—It may result from a bruise of the eyelid; from the introduction of foreign matters into the eye, as chaff, hayseed, dust, gnats, etc.; from exposure to cold; poisonous or irritating vapors arising from filthiness of stable. Dust, cinders, or sand blown into the eyes during transportation frequently cause conjunctivitis.

Symptoms.—A profuse flow of tears, closure of the eyelids from intolerance of light, retraction of the eyeball and corresponding protrusion of the haw, disinclination to move, diminution of milk secretion, etc. On parting the lids the lining membrane is found injected with an excess of blood, giving it a red and swollen appearance; the sclerotic, or white of the eye, is bloodshot and the cornea may be cloudy. If the disease advances, keratitis results, with its train of unfavorable symptoms.

Treatment.—Careful examination should be made to discover particles of chaff, etc., which may have lodged in the eye, and upon the discovery of such a cause prompt removal is indicated. This may be accomplished by flushing the eye with warm water by means of a syringe, or, if the foreign substance is adherent to the eyeball or lid, it may be scooped out with the handle of a teaspoon or some other blunt instrument. To relieve the congestion and local irritation, a wash composed of boracic acid in freshly boiled water, 20 grains to the ounce, or acetate of zinc, 5 grains to the ounce of pure soft water, may be used, to which may be added 20 drops of laudanum. A few drops of this should be placed in the eye with a camel's-hair pencil or soft feather three or four times daily. The animal should be placed in a cool, darkened stable; then a cloth folded into several thicknesses should be fastened to the horns in such manner as to reach below the eyes. This should be kept wet with cold water during the day and removed at night. If there is much fever and constitutional disturbance, it becomes advisable to administer 1 pound of Epsom salt dissolved in 1 quart of water.

INFECTIOUS CATARRHAL CONJUNCTIVITIS (SPECIFIC OPHTHALMIA).

This generally appears in an enzootic or epizootic form and affects a considerable number in the herd. It is distinctly a contagious disease and may be brought into a previously healthy herd by one infected animal. It may continue in a herd for a season or for several years, affecting all newly purchased animals. It is seldom seen in the winter months. It affects old and young animals alike.

Symptoms.—This form of catarrh conjunctivitis is characterized chiefly by a mucopurulent discharge from the eyes, an intense degree of inflammation of the mucous membrane, accompanied with swelling of the eyelids and an early opacity of the cornea. The flow of tears is mixed with pus, sometimes streaked with blood, and the skin of the face is kept moist and soiled. The eyes are kept continually closed. The implication of the cornea in the disease frequently blinds the animal for a time, and occasionally suppurative keratitis, ulcers of the cornea, or staphyloma supervene. The attack is marked from the onset by fever, partial loss of appetite, partial loss of milk, suspended rumination, and separation from the herd.

Treatment.—The animal should be housed in a cool, dark stable, supplied with plenty of fresh water to drink and soft, succulent feed. Administer 1 pound of Epsom salt—if a very large animal, use 1-1/2 pounds—dissolved in 2 or 3 pints of water. For an eyewash, take boracic acid, 1 dram, and pour 4 ounces of boiling water over it. Use this as often as is convenient, applying it directly to the eye. In the majority of cases improvement becomes manifest in a few days, and the eye becomes clear and free from inflammation in 10 days or 2 weeks. Where the disease develops ulceration of the cornea, or well-marked, deep-seated keratitis, the treatment recommended for those conditions should be adopted.

Prevention.—Whenever this affection appears in a herd all the unaffected animals should be moved to fields which possess a different character of soil and feed. The water should also be changed, especially if they have been obtaining it from a stagnant pond.

KERATITIS (CORNEITIS).

This is an inflammation of the cornea proper, although the sclerotic at the corneal border becomes involved to some extent. It may be divided into diffuse and suppurative.

Causes.—The cornea constitutes the most prominent portion of the eyeball, hence it is subject to a variety of injuries—scratches, pricks, contusions, lacerations, etc. Inflammation of the cornea may also be due to the extension of catarrhal conjunctivitis or intraocular disease, and it may occasionally occur without any perceptible cause.

Symptoms.—Diffuse keratitis is characterized by an exudation into and an opacity of the cornea. The swelling of the anterior part of the eyeball may be of an irregular form, in points resembling small bladders, or it may commence at the periphery of the cornea by an abrupt thickening, which gradually diminishes as it approaches the center. If the whole cornea is affected, it has a uniform gray or grayish-white appearance. The flow of tears is not so marked as in conjunctivitis, nor is the suffering so acute, though both conditions often exist together. Both eyes usually become affected, unless it is caused by an external injury.

In favorable cases the exudate within the cornea begins to disappear within a week or 10 days, the eye becomes clearer and regains its transparency, until it eventually is fully restored. In unfavorable cases blood vessels form and are seen to traverse the affected part from periphery to center, vision becomes entirely lost, and permanent opacity (albugo or leucoma) remains. When it arises from constitutional causes recurrence is frequent, leaving the corneal membrane more cloudy after each attack, until the sight is permanently lost.

Suppurative keratitis may be a sequel of diffuse keratitis; more commonly, however, it abruptly becomes manifest by a raised swelling on or near the center of the cornea that very soon assumes a yellow, turbid color, while the periphery of the swelling fades into an opaque ring. Suppurative keratitis is seldom noticed for the first day or two—not until distinct pus formation has occurred. When it is the result of diffuse keratitis, ulceration and the escape of the contained pus is inevitable; otherwise the pus may be absorbed. When the deeper membranes covering the anterior chamber of the eye become involved, the contents of this chamber may be evacuated and the sight permanently lost.

Treatment.—Place the animal in a darkened stable, give green or sloppy feed, and administer 4 ounces of Glauber's salt (sulphate of soda) dissolved in a quart of water once a day. If the animal is debilitated a tablespoonful of tonic powder should be mixed with the feed three times a day. This may be composed of equal parts by weight of powdered copperas (sulphate of iron), gentian, and ginger. As an application for the eye, nitrate of silver, 3 grains to the ounce of soft water, with the addition of 1 grain sulphate of morphia, may be used several times a day. If ulceration occurs, it is well to dust powdered calomel into the eye twice daily, or apply to the eyelids a salve of yellow oxid of mercury, 5 per cent in lanolin. Some of this may go on to the cornea and beneath the lids. Apply twice daily. (See "Ulcers of the cornea.")

To remove opacity, after the inflammation has subsided, apply a few drops of the following solution twice a day: Iodid of potassium, 15 grains; tincture sanguinaria, 20 drops; distilled water, 2 ounces; mix.

Sometimes keratitis exists in a herd as a transmissible disease, spreading like infectious conjunctivitis. Calomel, applied to the eye, is especially useful in such cases.

ULCERS OF THE CORNEA.

An ulcer comes from erosion or is the consequence of the bursting of a small abscess, which may have formed beneath the delicate layer of the conjunctiva, continued over the cornea; or, in the very substance of the cornea itself, after violent keratitis, or catarrhal conjunctivitis. At other times it is produced by bruises, scratches, or other direct injury of the cornea.

Symptoms.—The ulcer is generally at first of a pale gray color, with its edges high and irregular, discharges instead of pus an acrid, watery substance, and has a tendency to spread widely and deeply. If it spreads superficially upon the cornea, the transparency of this membrane is lost; if it proceeds deeply and penetrates the anterior chamber of the aqueous humor, this fluid escapes, the iris may prolapse, and the lens and the vitreous humor become expelled, thus producing destruction of the whole organ.

Treatment.—It is of the greatest importance, as soon as an ulcer appears upon the cornea, to prevent its growing larger. The corroding process must be converted into a healthy one. For this purpose nothing is more reliable than the use of solid nitrate of silver. A stick of this medicine should be scraped to a point; the animal's head should be firmly secured; an assistant should part the lids; if necessary, the haw must be secured within the corner of the eye and then all parts of the ulcer should be lightly touched with the silver. After waiting a few minutes the eye should be thoroughly washed out with a very weak solution of common salt. This operation generally has to be repeated at the end of three or four days. If healthy action succeeds, the ulcer assumes a delicate fleshy tint, and the former redness around the ulcer disappears in proportion as the ulcer heals.

In superficial abrasions of the cornea, where there is no distinct excavation, this caustic treatment is not needed. The eye should be bathed several times a day with sulphate of zinc, 30 grains to half a pint of soft water, and protected against exposure to cold air and sunlight. Excessive ulceration sometimes assumes the form of fungous excrescence upon the cornea, appearing to derive its nourishment from loops of blood vessels of the conjunctiva. Under these circumstances the fungoid mass must be cut away and the wound cauterized with the nitrate of silver, or else the eye will soon be destroyed. When ulcers of the cornea appear indolent, with a tendency to slough, in addition to the treatment already prescribed, tonic powders of copperas, gentian, and ginger, equal parts by weight, should be given twice a day, mixed with the feed; dose, one tablespoonful.

STAPHYLOMA.

This is a disease of the eyeball, in which the cornea loses its transparency, rises above the level of the eye, and even projects beyond the eyelids in the form of an elongated, whitish, or pearl-colored tumor, which is sometimes smooth, at other times uneven.

Causes.—Inflammation is the only known cause, although it may not occur immediately; it frequently follows catarrhal conjunctivitis and keratitis as a sequela.

Treatment.—In a few cases restoration of sight may be effected by puncturing the projecting tumor and treating it afterwards with nitrate of silver in the same manner as prescribed for ulceration of the cornea. In some cases spontaneous rupture has occurred, and healing without any treatment at all.

CATARACT.

In cataract the crystalline lens becomes opaque and loses its transparency, the power of refraction is lost—the animal can not see.

Causes.—Cataract generally arises from a diminution (atrophy) or other change in the nutrition of the lens; it may occur as a result of inflammation of the deep structures of the eye. Cataract may be simple, or complicated with amaurosis, adhesions, etc.

Symptoms.—It is known by the whiteness or loss of transparency of the lens, although the pupil dilates and contracts. Sight may be totally lost; however, evidence is usually manifested that the animal distinguishes light when brought out of a darkened stable. For the most part the formation of cataract takes place slowly, the cases in which it originates very quickly being but few.

Treatment.—There is only one method for the treatment of cataract—a surgical operation for the removal of the lens; but this is not advisable, for the sight can not be perfectly restored, and objects would be seen imperfectly without the aid of glasses.

AMAUROSIS.

This is a paralysis of the nerve of sight or the expansion of the retina.

Causes.—This is the result of concussion from a blow upon the forehead, fracture of bone over the eye (causing downward pressure), rheumatic inflammation of the optic nerve, or from extension of deep inflammation of the eye involving the retina. It sometimes occurs as the result of excessive loss of blood or of great debility.

Symptoms.—In this disease observation is seldom made until the animal in its gait and by its action indicates blindness. Generally both eyes are affected. The eyeball remains clear, and the pupil is permanently dilated. No response to light is manifested.

Treatment.—If caused by debility, loss of blood, or associated with rheumatism, general blood tonics may be given in the feed, namely, powdered sulphate of iron, 1 dram; gentian, 2 drams; nux vomica, one-half dram; to be given twice a day. In cases of rheumatism, one-half ounce of saltpeter may be added.

FILARIA OCULI (WORM IN THE EYE).

Filaria oculi (provisionally taken as the larva of F. cervina) is a small white worm, found swimming in the aqueous fluid in the anterior chamber. It may be apparently harmless for a long time, but will eventually induce keratitis with inflammatory exudations.

Treatment.—The cornea may be punctured at its upper and outer margin, and the worm squeezed out with the aqueous humor. The latter will be formed again. This operation results disastrously unless the greatest care and skill are employed.

CORNEAL DERMATOMA (HAIRY TUMOR ON THE EYEBALL).

In a few instances this has been seen as a congenital growth. The tumor arises from the cornea or the sclerotic, covered by its respective membrane, with a growth of hair upon its surface. These tumors may be quite prominent or flattened, and are dark in color; the hair may protrude between the eyelids, giving the animal the appearance of having a double eyelid.

Treatment.—A surgical operation becomes necessary for their removal— one requiring a skilled operator.

STRABISMUS (SQUINTING).

This is a very rare affection among cattle. Strabismus may be either single or double—affecting one eye or both. It is caused by a paralysis, or a weakening of one of the straight muscles of the eyeball. Generally it is a congenital defect, and the squinting is toward the nose—strabismus convergens. It is best not to attempt to remedy the defect, as the risk in an operation is greater than the chances of success warrant.

PTERYGIUM.

This term is applied to a flesh-colored membrane, triangular in form, which most frequently grows from the inner angle of the eye and extends over the cornea, thus interfering with vision. It may grow from the outer angle, or even from either the superior or inferior hemisphere of the eyeball. The figure is invariably that of a triangle, with its base on the white of the eye and its apex more or less advanced over the cornea toward its center.

The distinguishing characteristics are the constancy of the triangular form, and the facility with which the whole of it may be taken hold of with a pair of forceps and raised into a fold on the cornea. Every other kind of excrescence attached to this membrane continues firmly adherent to it, and can not be folded and raised from the surface of the cornea in any manner whatever.

Treatment.—Raise the fold and dissect it away from all points of attachment.

TRICHIASIS (INVERSION OF THE EYELASHES).

In the simplest form the eyelashes bend inwardly, touching the eyeball, causing irritation and simple conjunctivitis. It may be also associated with entropion.

Treatment.—The offending eyelashes should be cut off or pulled out. In case the natural growth of the eyelashes is directed inward, an operation similar to that for entropion becomes necessary.

ENTROPION (INVERSION OF THE EYELID).

In inversion of the eyelid the eyelashes soon irritate the anterior face of the cornea and produce more or less inflammation and opacity. The inversion may be due to the growth of a tumor within or without the lid, to abscess, laceration, or injury, causing the lid to lose its natural conformity to the eyeball, ulcerations, etc. Surgical interference in either case becomes necessary to restore the lid to its natural direction.

ECTROPION (EVERSION OF THE EYELID).

This serves to injure the eye by permitting dust or other foreign substances to enter the eye and interferes with the natural removal of them.

Treatment.—A delicate surgical operation—the removal of an elliptic section of the palpaebral conjunctiva—may remedy the defect.

TUMORS OF THE EYELIDS.

Occasionally tumors form upon or within the substance of the eyelid. They may be of a fibroid nature and arise from the follicles of the hair as sebaceous tumors or may be in the form of an abscess. In debilitating diseases the lids sometimes become swollen and puffy, a condition which may possibly be taken for the growth of a tumor. This generally disappears with the improvement of the health of the animal. Warts not uncommonly appear on or about the eyelids of cattle.

Treatment.—The removal of a tumor in the vicinity of so delicate an organ as the eye should not be attempted by anyone not qualified to perform the operation.

LACERATION OF THE EYELID.

This accident is not uncommon where cattle are fenced in by barbed wire; an animal may be caught under the eyelid by the horn of another, or the laceration may occur in the stable by means of a projecting nail or splinter of wood.

Treatment.—The edges of the wound should be brought together closely and correctly, by means of pins pushed through very nearly the whole thickness of the lid, extending through each lip of the torn part; then a waxed silk or linen thread must be wound over each end of the pin, crossing the torn line in the form of the figure 8 (Pl. XXVII, fig. 9); the pins should be placed about three-eighths of an inch apart. The projecting ends of the pins should be cut off close to the ligature, and the parts kept anointed with vaseline, to which 2 per cent of compound cresol has been added. In place of a pin suture, silver wire, catgut, or strong linen thread may be used in the way of an ordinary suture.

FOREIGN BODIES IN THE EYE.

Splinters of wood, hedge thorns, pieces of cornstalk or leaves, stems of hay or straw, twigs of trees, or weeds may penetrate into the eye, break off, and remain, causing inflammation, blindness, abscess, etc. These substances may penetrate the eyeball, but more frequently they glide off and enter between the eye and the ocular sheath.

Treatment.—Their removal becomes often a very difficult task, from the fact that the organ is so extremely sensitive, and the retracting power so strong as to necessitate casting the animal, or even the administration of sufficient chloroform to render it completely insensible. The removal, however, is of paramount importance, and the after treatment depends upon the extent and location of the injury—cold water compress over the injured eye, the application of mild astringent and cooling washes, such as acetate or sulphate of zinc, 5 grains to the ounce of water. When there is extreme suffering from pain a solution of atropia or morphia, 5 grains to the ounce of water, may be dropped into the eye, alternating with the cooling wash several times a day. When abscesses form within the orbit a free opening must be maintained for the discharge of pus. In deep penetrating wounds of the eye there is a great tendency to the formation of a fungous growth, which often necessitates the enucleation of the whole eyeball.

ORBITAL AND PERIORBITAL ABSCESS.

Orbital abscess may form outside the globe and within the orbital sheath, as the result of a previous wound of the parts or from fracture of the bony orbit, etc. Periorbital abscess commences outside the ocular sheath, beneath the periosteal membrane covering the bone, and is usually the result of a disease or fractured bone which enters into the formation of the orbital cavity.

Symptoms.—Orbital abscess is manifested by a pushing forward of the eyeball (exophthalmos), a swelling of the conjunctiva and eyelids. The bulging out of the eye is in proportion to the size of the abscess; the movement of the eye is fixed, due to the painfulness of any voluntary movement of the eyeball. Periorbital abscess generally pushes the eye to one side; otherwise the symptoms are similar to the foregoing. The pain generally is very great; paralysis of the nerve of sight may occur, and death may be caused by the abscess extending to the brain.

Treatment.—The treatment for either orbital or periorbital abscess is the same as that for abscess occurring in any other part of the body—a free opening for the escape of imprisoned pus. This should be made as soon as the true nature of the disease is recognized. Afterwards antiseptic injections may be needed to stimulate healthy granulation and to prevent septic infection of the ocular membranes. For this purpose a saturated solution of boric acid or listerine 1 part to 10 of water may be used. When the fever runs high, Glauber's salt (sulphate of soda) may be given in 4-ounce doses once a day. The animal should be kept in a darkened stable, on soft or green feed.

FRACTURE OF THE ORBIT.

This accident occasionally occurs among belligerent animals, or as the result of blows delivered by brutal attendants. The orbital process above the eye may be entirely crushed in, pressing down upon the eyeball. In such an event the depressed bone should be elevated into its proper place, and if it fails to unite it may have to be removed with saw or chisel. The margin of the orbit may be crushed at any point and cause periorbital abscess, or necrosis may result from the presence of a splinter of bone or the excessive destruction of bone. In all cases of fracture the animal should be kept by itself until the injured part heals.

NECROSIS OF THE BONY ORBIT.

As the result of fracture of the margin of the orbit a part of the injured bone may become necrosed (dead), and periostitis and periorbital abscess will follow as a consequence. The discovery of this disease will at first resemble abscess, but on making an examination with a probe after the abscess is open we find the bone rough and brittle at the point of disease. The discharge has a peculiar fetid odor, and is often mixed with blood.

Treatment.—The affected bone must be laid bare and all diseased portions removed by scraping or, if necessary, with saw or chisel, disregarding the extent of the injury or the size of the wound necessary to be inflicted. A large portion of the bony orbit may be removed without serious danger to the eye, provided the eyeball itself has not been previously affected by the disease or involved in the original injury.

TUMORS OF THE ORBIT.

A fungous tumor of the eyeball or orbit occasionally appears, which is designated fungus haematodes. This may arise without any appreciable cause, or as the result of a wound. It frequently commences within the eyeball as a small, red mass, eventually bursts through, and pushes its way outside the orbit as a large, dark-red mass, bleeding at the slightest touch. It has a peculiar, fetid odor, and early in its appearance destroys sight, involving all the contents of the orbit, not infrequently the bony wall itself.

Unless the tumor is totally removed in its early stage of growth, together with the eyeball, the disease will eventually cause emaciation and death of the animal. The enucleation of the eyeball should not be undertaken by anyone unacquainted with the anatomical structures involved in such an operation. When the operation is performed early enough the result is generally satisfactory.

Bony tumors of the orbit, the result of bruises, fractures, etc., are occasionally present in cattle. They may encroach upon the contents of the orbit, causing paralysis of the optic nerve—the condition known as amaurosis—or by pressure upon the posterior surface of the eyeball force it forward, or produce atrophy (shrinking). They may displace the eye in any direction, with or without disturbing vision.

Fibrous tumors growing within the orbit will produce symptoms similar to those of bony tumors.

Treatment.—When the outlines of the tumor, whether fungoid, bony, or fibrous, can be detected, an operation for its removal should be undertaken as soon as the sight of the eye is in any manner disturbed.

DISLOCATION OF THE EYEBALL.

The eyeball may be torn out of its socket by the horns of another animal, or it may be crowded out with the blunt end of a club, cane, or probe in the hands of a brutal attendant.

Treatment.—When the optic nerve is not lacerated and the retractor muscles at the back of the eye are intact, an attempt at reduction is advisable. This, however, must follow very soon after the injury—before swelling takes place. Divide the outer corner of the eyelid to enlarge the orifice, then by pressure with the fingers of both hands placed upon the sides of the eye the ball may be put into its place. Apply a firm compress over the injured eye and keep it constantly wet with cold water containing 1 dram of sugar of lead to each quart.

If the attempt at reduction proves unsuccessful the artery at the back of the eye should be ligated, and then the whole mass cut off as deep within the orbit as possible. The orbital cavity, after washing it out with a 3 per cent solution of carbolic acid or compound cresol, should be packed daily with fresh absorbent cotton.

INFLAMMATION AND ENLARGEMENT OF THE HAW.

The haw, or membrana nictitans, is subject to inflammation and swelling from the extension of conjunctivitis, or direct injury by foreign substances. It presents a red, swollen appearance, accompanied with considerable pain and a profuse flow of tears. A slight scarification with a sharp knife and the application of a cooling lotion, such as is recommended for conjunctivitis, will soon reduce the swelling and restore it to its normal function.

There is, however, a tendency for an inflammation of this membrane to take on a chronic character, which may eventually result in a permanent enlargement, resembling a tumor. When it attains sufficient size to protrude itself permanently over the eye, or project between the lids so as to obstruct the sight, its removal may become necessary. A threaded needle is passed through the body of the enlarged mass, by which the membrane is drawn out as far as possible, then with a blunt pair of scissors it may be dissected away from its attachments. The eye is afterwards treated with simple cooling lotions.



DISEASES OF THE EAR.

By M. R. TRUMBOWER, D. V. S.

[Revised by Leonard Pearson, B. S., V. M. D.]

Diseases of the ears of cattle are not very common, for the reasons probably that they are not subjected to the brutality of drivers so much as horses and that the horns to a great extent protect them against external violence.

OTITIS (INFLAMMATION OF THE INTERNAL EAR).

Inflammation of the deep part of the ear is often difficult to recognize in cattle. It may be caused by disease of bone in that region, from blows inflicted by drivers, or from injury by other cattle. Occasionally the ear becomes involved in actinomycosis (lumpy jaw), or the inflammation may be the result of a tuberculous affection.

Symptoms.—The animal will hold its head to one side, or shake it, while the ear itself is held immovable. The movement of the jaws in eating usually gives rise to a manifestation of pain; the base of the ear may be feverish and swollen, and very sensitive to the touch. If the inflammation has advanced to a suppurative stage, offensive matter will flow from the ear.

Treatment.—At first, hot fomentations to reduce pain and fever, followed by a sharp blister below the ear. Laudanum, 1 part to 10 of sweet oil, may be injected into the ear to relieve pain and to soften the secretions. If there is a discharge from the ear, it should be thoroughly washed out by injecting warm soapsuds until all the matter has been washed away; then inject the following mixture twice a day: Sulphate of morphia, 20 grains; water, 1 pint; glycerin, 4 ounces.

ABSCESS.

Abscesses, caused by contusions, sometimes form about the base of the ear, either inside or outside. A serous cyst is found occasionally between the cartilage and the skin on the base of the ear, which may be from a similar cause.

Treatment.—With the knife make a free incision into the most prominent part of the abscess or cyst, then, with a syringe, wash out the sac with carbolized water. If the abscess recurs, open it again, wash it out, and inject tincture of iodin, or fill it with iodoform.

FUNGOID GROWTHS.

As a result of laceration or wound of any kind, fungous growths, characterized by a raw, bleeding, granulating surface, with a tendency to become pendulous, may develop on the ear.

Treatment.—The whole tumor or diseased structure should be cut away, and the wound treated daily with a dressing of carbolized cosmoline or turpentine and sweet oil, 1 part of the former to 4 of the latter.

FOREIGN BODIES IN THE EAR.

Bugs have been known to gain entrance into the ears of animals. I once removed an acorn from the ear of a cow that had been roaming in the woods; also pieces of wood from a stanchion may be lodged accidentally in the ear.

Symptoms.—There is usually a continuous uneasiness or frequent shaking of the head, occasionally the manifestation of exceedingly great pain. The animal may rub the head and ear against trees or other objects in an endeavor to dislodge the offending body.

Treatment.—A careful examination reveals the cause, which may be removed with a pair of forceps or scraped out with a hairpin or piece of wire bent at one end. If much inflammation exists, the ear may be swollen so that the foreign substance is hidden from sight; then a probe may be inserted to feel for the object, which, when found, should be removed, even if it becomes necessary to split the ear at the base. Afterwards treat the ear with frequent warm water fomentations and the injection of soapy water or oil and water.

SCURFY EARS.

Cattle are subject to scurfy ears, which may be owing to a generally morbid condition of the skin, or may be confined to the ears alone. The affected animal shows an inclination to rub the ear; thick scales, which sometimes have the appearance of hard, dry, horny scales, of scurf collect on it. This condition is chiefly caused by a faulty secretion of the sebaceous glands of the ear. Thoroughly clean the ear with a stiff brush, then anoint it, so far as affected, with vaseline 4 parts to 1 part of white precipitate ointment. If the scurfy ears are only a part of a general scurfiness of the skin, the condition of the animal needs attention. (See "Pityriasis," p. 329.)

FROSTBITE.

It is not uncommon among young cattle which are poorly nourished and exposed outdoors to storms and extreme cold to suffer frostbite of the ear, which may constitute actual freezing of the part.

Symptoms.—Frostbite presents naturally every degree of severity from the mere chilling of the tip of the ear to positive freezing and death of a portion. In a day or two after the freezing has occurred the ear becomes swollen and very painful; the dead part remains cold and begins to shrivel; a line of separation then forms between the inflamed and the dead or dying portion, and finally the piece destroyed drops off, leaving a raw healing surface. When the ear is only slightly affected by the cold, an excoriation or peeling off of superficial skin takes place, accompanied with some pain and itching.

Treatment.—A good liniment for frozen ears is a mixture of turpentine, ammonia, and chloroform, of each 1 part, added to 6 parts of sweet oil. Rub this on the ear several times a day. It will relieve pain and stimulate the circulation, thus favoring a recovery of the injured structures.

LACERATIONS OF THE EAR.

Aggressive dogs are the most frequent cause of lacerated ear, generally leaving a torn, ragged edge and bruised cartilage.

If the wound is extensive, a trimming of the ragged edges becomes necessary; then the edges should be fastened together with silver wire, catgut, or strong, thick, linen thread, taking a deep hold, and pine tar applied.

DISEASE OF THE CARTILAGE AND NECROSIS.

Occasionally the cartilages of the ear become affected, usually the result of a deep bruise; pus forms, burrows under the skin, and may find a discharge from any part of the ear more or less distant from the seat of the disease. When the cartilage has been extensively injured, pieces of it may become dead (necrosed) and dissolve, to be carried away with the pus, or it may lead to extensive sloughing and the formation of numerous running sores. In the disease of the cartilage there is seldom much swelling or great pain. The discharge is usually very offensive, and occasionally streaked with blood. Whenever there is a long-continued, persistent discharge from one or more openings in the ear, disease of the cartilage may be suspected.

Treatment.—The sinus formed by the passage of matter should be probed and searched to the bottom for the presence of a foreign substance or the evidence of decaying cartilage. When the probe touches necrosed cartilage it will feel like a piece of dry leather or partially softened wood. A counter opening must then be made at this place, and all diseased cartilage cut away with the knife. The subsequent treatment consists in keeping the artificial wound open for the discharge of pus, and the injection of chlorid of zinc, 5 grains to the ounce of water, once or twice a day, until the wound is healed.

ENCHONDROMA OF THE EAR.

This is an excessive growth of cartilage, found at the base of the ear in the form of a hard, painless tumor, firmly attached to the movable ear. The only recourse for its removal is the knife in the hands of one acquainted with the anatomy of the part involved in the operation.



INFECTIOUS DISEASES OF CATTLE.

Revised by JOHN R. MOHLER, A. M., V. M. D.,

Chief, Bureau of Animal Industry.

GENERAL INTRODUCTION.

The importance, to the farmer and stock raiser, of a general knowledge of the nature of infectious diseases need not be insisted on, as it must be evident to all who have charge of farm animals. The growing facilities for intercourse between one section of a country and another, and between different countries, cause a wide distribution of the infectious diseases once restricted to a definite locality. Not only the animals themselves, but the cars, vessels, or other conveyances in which they are carried may become agents for the dissemination of disease. The growing tendency of specialization in agriculture, which leads to the maintenance of large herds of cattle, sheep, and hogs, makes infectious diseases more common and more dangerous. Fresh animals are being continually introduced which may be the carriers of disease from other herds, and when disease is once brought into a large herd the losses become very high, because it is difficult, if not impossible, to check it after it has once obtained a foothold.

These considerations make it plain that only by the most careful supervision by intelligent men who understand the nature of infectious diseases and their causes in a general way can these be kept away. We must likewise consider how incomplete our knowledge concerning many diseases is, and probably will be for some time to come. The suggestions and recommendations offered by investigators, therefore, may not always be correct, and may require frequent modification as our information grows more comprehensive and exact.

An infectious disease may be defined as any malady caused by the introduction, into the body, of minute organisms of a vegetable or animal nature which have the power of indefinite multiplication and of setting free certain peculiar poisons which are chiefly responsible for the morbid changes.

This definition might include diseases caused by certain animal parasites, such as trichinae, for example, which multiply in the digestive tract, but whose progeny is limited to a single generation. By common consent the term "infectious" is restricted to those diseases caused by the invasion and multiplication of certain very minute unicellular organisms included under the general classes of bacteria and protozoa. Nearly all the diseases of cattle for which a definite cause has been traced are from bacteria. Among these are tuberculosis, anthrax, blackleg, and tetanus (or lockjaw). Some diseases, such as Texas fever and nagana, are traceable to protozoa, while others, like actinomycosis and aspergillosis, are caused by fungi. Those diseases of which the cause is unknown or imperfectly worked out are pleuropneumonia, rinderpest, foot-and-mouth disease, rabies, cowpox, malignant catarrh, and dysentery.

Bacteria may be defined as very minute, unicellular organisms of a plantlike character. Their form is very simple, as may be seen from an inspection of the various species depicted on Plate XXVIII. The description of these figures will be found on page 360. The magnification there given will furnish the reader some idea of their very minute size. They multiply in two ways. The bacterium elongates and then divides in the middle to form 2 daughter cells. These go through the same process at once, and thus 4 cells are produced. The division of these leads to 8, the division of 8 to 16, and so on indefinitely. The rapidity with which this multiplication takes place depends upon the nature of the bacterium. The bacillus of tuberculosis multiplies very slowly, while that of anthrax does so with great rapidity, provided both are in the most favorable condition. Another mode of reproduction, limited to certain classes of bacteria, consists in the formation of a spore within the body of the bacterium. Spore formation usually takes place when the conditions pertaining to the growth of the bacteria become unfavorable. The spores are much more resistant to destructive agents than the bacteria which produced them. The anthrax spore may live several years in a dried state, but the anthrax bacillus perishes in a few days under like conditions. This matter will be referred to again when we come to discuss the subject of disinfection.

Of the protozoa which cause disease very little is at present known. One which produces Texas fever is pictured on Plate XLV, in figs. 4 and 5. These parasites have a more complex life history than bacteria; and as they can not be grown in artificial media, their thorough investigation is at present hampered with great difficulties.

The differences in the symptoms and lesions of the various infectious diseases are due to differences in the respective organisms causing them. Similarly the great differences observed in the sources from which animals become infected and the manner in which infection takes place are due to differences in the life history of these minute organisms. Much discussion has taken place of late years concerning the precise meaning of the words "infection" and "contagion."

* * * * *

VARIOUS BACTERIA WHICH PRODUCE DISEASE IN CATTLE. DESCRIPTION OF PLATE XXVIII.

The bacteria on this plate are partly from tissues, partly from cultures, and stained artificially with aniline colors (fuchsin or methylene blue). Figs 6 and 7 are copied from Fraenkel and Pfeiffer's atlas. All but fig. 7 are magnified 1,000 times; fig. 7, 500 times.

Fig. 1. Bacteria from pneumonia in cattle. These are also the cause of hemorrhagic septicemia and are closely related to swine-plague bacteria. These bacteria were drawn from a piece of spleen pulp (rabbit).

Fig. 2. Micrococci (streptococcus) which produce inflammation of the lining membranes of the abdomen, thorax, heart, brain, and joints. Frequently associated with the preceding bacteria in abscesses.

Fig. 3. Micrococci (staphylococcus) which produce inflammation and suppuration; also pyemia.

Fig. 4. Bacilli of blackleg. The pale oval bodies as well as the light spots in one end of the bacilli represent spores.

Fig. 5. Bacilli which produce tetanus or lockjaw. The light spot in the enlarged end of each rod represents a spore.

Fig. 6. Bacilli of tuberculosis. Microscopic sections of a pearly nodule from the lining membrane of the chest cavity. The bacilli are stained red and appear as small straight rods within the cells of the nodule or tubercle.

Fig. 7. Bacilli of anthrax. Bacilli from the spleen of a mouse inoculated with a culture. The bacilli were obtained from the blood of a cow which died of anthrax in Mississippi. The bacilli appear as rods stained blue. The round bodies are blood corpuscles, also stained artificially.



* * * * *

These words, however, are now wholly inadequate to express the complex processes of infection, and it may be said that each species of bacterium or protozoon has its own peculiar way of invading the animal body, differing more or less from all the rest. There are, however, a few broad distinctions which may be expressed with the help of these old terms. Infection, as laid down above, refers at present in a comprehensive way to all microorganisms capable of setting up disease in the body. Some microorganisms are transmitted directly from one animal to another, and the diseases produced may be called contagious. Among these are included pleuropneumonia, rinderpest, foot-and-mouth disease, rabies, cowpox, and tuberculosis. Again, certain organisms are perhaps never transmitted from one animal to another, but may come from the soil. Among these are tetanus, blackleg, anthrax to a large extent, and perhaps actinomycosis in part. These diseases, according to some authorities, may be called miasmatic. There is a third class of infectious diseases, the specific bacteria of which are transmitted from one animal to another, as with the contagious diseases, but the bacteria may, under certain favorable conditions, find food enough in the soil and in the surroundings of animals to multiply to some extent after they have left the sick animal and before they gain entrance into a healthy one.

This general classification is subject to change if we take other characteristics into consideration. Thus tuberculosis, because of its insidious beginning and slow course, would not by many be considered contagious in the sense that foot-and-mouth disease is; yet, in either case, the bacillus must come from preexisting disease. The disease of rabies, or hydrophobia, is not contagious in the sense that rinderpest is, because the virus of rabies must be inoculated into a wound before it can take effect; yet, in both cases, the virus passes without modification from one animal to another, though in different ways.

Again, all the diseases under the second group, which seem to come from the soil and from pastures, are in one sense contagious in that the virus may be taken from a sick animal and inoculated directly, with positive results, into a healthy animal. Other illustrations may be cited which show that these old terms are not in themselves satisfactory. There are so many conditions which enter into the process of infection that no single classification will give a sufficiently correct or comprehensive idea of it. These statements will be easily understood if the different infectious diseases in the following pages are studied with reference to the way or ways in which each disease may be contracted. Enough has been said, therefore, to show that if we wish to make ourselves acquainted with the dangers of any given disease, we must study it and not rely upon any single work to tell the whole story.

Infectious diseases have, as a general rule, a period of incubation, which comprises the time elapsing between the exposure to the infection and the actual appearance of the disease. This period varies with the malady. The most common symptom of this class of diseases is fever. The severity of the fever is measured by the temperature of the animal; this is readily and accurately ascertainable by the clinical thermometer. (See Pl. III, fig. 1.) The other symptoms are variable and depend upon the particular organ or organs most implicated. Loss of appetite, cessation of rumination and milk secretion, and general dullness are symptoms quite invariably present in most infectious diseases.

During the course of infectious diseases secondary diseases or complications may arise which are largely caused by bacteria other than those producing the original malady. These complications are often so severe as to become fatal. In general it may be stated that they are due to filthy surroundings, and hence cleanliness may become an important aid to recovery.

The treatment of infectious diseases is given under each malady so far as this is allowable or advisable. These diseases are not, as a rule, amenable to treatment. When the symptoms have once appeared the disease is liable to run its course in spite of treatment, and if it is one from which animals usually recover, all that can be done is to put them into the most favorable surroundings. Many infectious diseases lead sooner or later to death, treatment is useless so far as the sick are concerned, and it may be worse than useless for those not yet infected. All animals suffering with infectious diseases are more or less directly a menace to all others. They represent for the time being manufactories of disease germs, and they are giving them off more or less abundantly during the period of disease. They may infect others directly or they may scatter the virus about, and the surroundings may become a future source of infection for healthy animals. This leads us to the subject of prevention as the most important of all which claim our attention. In this place only a few general remarks will suffice to bring the subject before the reader.

The most important thing is to keep disease away from a herd or farm. To do this all sick or suspicious animals should be avoided. A grave form of disease may be introduced by apparently mild or trivial cases brought in from without. It is generally conceded that continual change and movement of animals are the most potent means by which infectious diseases are disseminated.

With some cattle diseases, such as anthrax, rinderpest, and pleuropneumonia, preventive inoculation is resorted to in some countries. This may be desirable when certain diseases have become established in any locality so that eradication is impossible. It should not be practiced in territories where a given disease may still be extirpated by ordinary precautions. Preventive inoculation is applicable to only a few maladies, and therefore its aid in the control of diseases is limited.

When an infectious disease has gained foothold in a herd the course to be pursued will depend upon the nature of the malady. A good rule is to kill diseased animals, especially when the disease is liable to run a chronic course, as in tuberculosis. The next important step is to separate the well from the sick by placing the former on fresh ground. This is rarely possible; hence the destruction or removal of the sick, with thorough disinfection of the infected locality, is the next thing to be done. As to the disinfectants to be used, special directions are given under the various diseases, to which the reader is referred. Here we will simply call attention briefly to the general subject.

DISINFECTION AND DISINFECTANTS.

Disinfection consists in the use of certain substances which possess the power to destroy bacteria or their spores, or both. Those which are cheapest and most available for animal diseases are ordinary freshly slaked lime or unslaked in powder, chlorid of lime, crude carbolic acid, corrosive sublimate, formaldehyde gas, formalin, and compound cresol solution.

(1) Slaked lime is perhaps the most easily procured, but its disinfecting power is limited. While it is capable of destroying all bacteria in their vegetative state, it is unable to destroy such spores as those of anthrax and blackleg. It is probable, however, that in incrusting spores it may destroy their vitality sooner or later. It is regarded as safe practice to use only spore-destroying substances for the virus of those diseases of which we have no definite knowledge. Nevertheless, in the absence of other disinfectants, lime is very useful. It may be employed as a whitewash on wood and stone and sprinkled as a dilute wash or in powder over yards, manure heaps, and over carcasses before they are buried, and over the ground on which they have lain to prevent other animals from carrying the infection away.

(2) Chlorid of lime is more efficient than simple slaked or unslaked lime, as it destroys spores. It is the ordinary bleaching powder of commerce and is quite unstable, hence old preparations, unless sealed, are of little value. A 5 per cent solution is sufficiently strong for all spore-bearing bacteria (3 ounces in 2 quarts of water). It may be efficiently applied to the walls and floor of an infected stable by mixing with limewash in the proportion of 6 ounces of the lime to each gallon of limewash. The ceilings and those portions of the walls which can not be reached should be disinfected by means of chlorin gas liberated from the chlorid of lime by crude carbolic acid. This is accomplished by making a cone of 5 or 6 pounds of chlorid of lime, in the top of which a deep crater is made for the placement of from 1 to 2 pints of crude acid. The edge of the crater is thereupon pushed into the fluid, when a lively reaction follows. The fumes of chlorin are strongly irritating to the respiratory tract and therefore all live stock should be removed before the work is started. Owing to the heat generated, it is advisable to place the lime in an iron crucible and to have nothing inflammable within a radius of 2 feet. The number and location of these cones of chlorid of lime depend on the size and structure of the building to be disinfected. As a rule, it may be stated that chlorin gas liberated from the above-sized cone will be sufficient for disinfecting 5,200 cubic feet of air space.

(3) Crude carbolic acid. The ordinary purified carbolic acid is too expensive to be used on a large scale, and the crude produce is a very good substitute. This is made more powerful by mixing with it an equal volume of commercial sulphuric acid. While the sulphuric acid is being added to the crude carbolic acid much heat is evolved, and if the glass jar in which the two are mixed is placed in cold water the resulting product is said to have a higher disinfecting power. The mixture is added to water enough to make a 5 per cent solution (about 7 ounces to 4 quarts of water). This is strong enough for all purposes. It may be kept in wood or glass, but not in metal, owing to the corroding action of the acid. It should be used freely on woodwork and on infected floors, and a force pump of the kind used by orchardists is very convenient as a means of applying the disinfectant. If the solution is warm when applied, it will penetrate the woodwork better than when cold, especially if the spraying is done during cold weather. The addition of air-slaked lime in any quantity that will dissolve in water to the above solution (say 1-1/2 pounds of lime to 7 ounces of crude carbolic acid to each gallon of water) is preferred by many, as it makes any neglected places at once visible and leaves cleaner and better air within the buildings. In most cases in which its application becomes desirable—and this rule should apply to all disinfections—the disinfected stables, stalls, etc., should remain vacant as long as possible before cattle are again stabled therein.

(4) Mercuric chlorid, or corrosive sublimate, is a powerful disinfectant, but it is likewise very poisonous; hence its uses are limited. Cattle are especially susceptible to its action and caution must be used in its application. A solution of one-tenth of 1 per cent is usually sufficient (1 ounce to 8 gallons of water). It should not be placed in wooden pails, which would form the tannate of mercury, a weak antiseptic; nor, owing to its corrosive action, should expensive metal pails be used. Agate vessels or tin pails are to be preferred. All solutions should be labeled "poison," and to avoid accidents none should be kept on hand.

(5) Formalin and formaldehyde gas have been found very efficacious as sanitary agents. Formalin is the commercial name for the 40 per cent solution of formaldehyde gas in water, and is one of the most powerful antiseptic and disinfectants that we possess. Solutions of this strength are manufactured by different commercial houses and sold by the drug trade under the name of "formalose" and "formal." In this connection it should be mentioned that while the 40 per cent solution of formaldehyde gas and formalin are exactly the same thing, the former can be purchased at 33-1/3 to 64 per cent less than the latter. Formalin, diluted with water in the proportion of 1 pint to 30 parts of water, or 4 ounces to each gallon of water, may be applied, and it may thus be used as a wash or as a spray on all paints, metals, and woodwork, as well as on clothing and other fabrics, without injuring them. It may also be applied to floors, walls, and woodwork in whitewash by mixing 1 part to 30 parts of limewash, or 4 ounces to each gallon of limewash. Formalin has the appearance of water and in the strong solution is poisonous, but when diluted as recommended above it is not dangerous. The fumes given off by it, however, are very disagreeable and irritating to the eyes and nasal mucous membranes. One and one-half ounces of formalin added to 1 gallon of water is a valuable agent for the disinfection of the skin or septic wounds, but is somewhat painful and irritating to raw surfaces.

Formaldehyde is a gas which is soluble in 2-1/2 parts of water (40 parts of formaldehyde gas to 100 parts of water); this solution constitutes the formalin of commerce. The use of formaldehyde gas is in most cases impracticable for stable disinfection. In case the stable is not too large and can be made almost air-tight the generation of formaldehyde gas, after removing all the animals, will be found very serviceable. It penetrates all parts of the stable—the walls, crevices, floors, ceiling—and is probably the best fumigating disinfectant that we have.

Probably one of the most simple and practical methods of liberating this gas is by means of the chemical reaction which takes place when formalin is poured upon permanganate of potassium. For each 1,000 cubic feet of air space, 16-2/3 ounces of crystallized or powdered permanganate of potassium is placed in a wide-surfaced pan; 20 ounces of formalin is then poured upon it, and the stable immediately closed for a period of 12 hours or longer. This method is efficient only when it is possible to seal tightly the place to be disinfected, and should be used only by experienced persons.

(6) Some coal-tar products are cheap, effective, and easily applied disinfectants, their action being due to the carbolic acid and creosote in their composition. They may be used in 3 to 5 per cent solution. As a rule they form a milky solution in water.

(7) Compound solution of cresol (liquor cresolis compositus), now recognized as an official preparation, is composed of equal parts of cresol and linseed-oil-potash soap. The mixture is a thick, dark, amber-colored fluid which mixes readily with water in all proportions to form a clear, soap solution. It is an efficient disinfectant in a 3 or 4 per cent solution, and in this strength it may be applied in the same manner as a 5 per cent solution of carbolic acid.

When it is desired to apply one of these above-mentioned agents to the stable or barnyard, a preliminary cleaning up of all debris and litter is advisable, together with the scraping of the floor, mangers, and walls of the stable with hoes; also the removal of all dust and filth. This should be followed by the burning of all such accumulations, inasmuch as this material likewise contains the infectious principle and is best destroyed by heat. Heat may be applied to the surface of the affected pen, byre, or barnyard by means of a cyclone burner, which consists of a tank, pump, hose, and cyclone nozzle for spraying with paraffin (gas oil). The latter is ejected in the form of spray, which when ignited gives a very hot and effective flame to be applied to the infected ground. Where such burning is impracticable the surface soil of the yard and surroundings should be removed to a depth of 5 or 6 inches and then placed in a heap and thoroughly mixed with air-slaked lime. The fresh surface of the soil thus exposed may then be sprinkled with the disinfectant.

In addition to these artificial substances there are several natural sanitary agents of great importance as destroyers of virus. These are cleanliness, ventilation, drying, and sunshine. All virus, excepting such as may live in the soil, is killed sooner or later by drying and sunshine, and the importance of these factors in the daily life of animals need not be insisted on here. Finally, all sanitary measures which contribute to the healthfulness of animal surroundings are directly or indirectly inimical to disease germs, and all carelessness in the keeping of animals may be regarded as an ally of these destructive organisms.

CONTAGIOUS PLEUROPNEUMONIA.

[Pls. XXIX-XXXII.]

Definition and history.—This disease has been eradicated from the United States, and it is not probable that it will ever be seen in this country again. As, however, much interest was manifested in regard to it for a number of years, and as our cattle are still prohibited from some foreign markets on account of its previous existence here, the subject is treated at greater length than would otherwise be necessary.

The contagious pleuropneumonia of cattle is a specific, epizootic disease which affects bovine animals, and from which other species are exempt. It is characterized, when the disease results from exposure in the usual manner, by an inflammation of the lungs and pleurae, which is generally extensive, and which has a tendency to invade portions of these organs not primarily affected and to cause death of the diseased portion of the lung. This disease is frequently called the lung plague, which corresponds to its German name of Lungenseuche. In French it is spoken of as the peripneumonie contagieuse.

The history of the contagious pleuropneumonia of cattle can not be traced with any certainty to a period earlier than the beginning of the eighteenth century. No doubt it existed and ravaged the herds of Europe for many years and perhaps centuries before that time, but veterinary knowledge was so limited that the descriptions of the symptoms and post-mortem appearance are too vague and too limited to admit of the identification of the maladies to which they refer. It has been supposed by some writers that certain passages in the writings of Aristotle, Livy, and Virgil show the existence of pleuropneumonia at the time that their works were composed, but their references are too indefinite to be seriously accepted as indicating this rather than some other disease.

It seems quite plain that as early as 1713 and 1714 pleuropneumonia existed in Swabia and several Cantons of Switzerland. There are even clearer accounts of its prevalence in Switzerland in 1732, 1743, and 1765. In 1769 a disease called murie was investigated in Franche-Comte by Bourgelat which undoubtedly was identical with the pleuropneumonia of to-day. From that period we have frequent and well-authenticated accounts of its existence in various parts of Europe. During the period from 1790 to 1812 it was spread throughout a large portion of the Continent of Europe by the cattle driven for the subsistence of the armies, which marched and countermarched in all directions. It was generally prevalent in Italy in 1800. It appears to have been unknown, however, in the Department of the Nord, France, until 1826, but during the years from 1820 to 1840 it penetrated into most parts of that country. During the same period it was introduced into and allowed to spread over Belgium and Holland.

This contagion is said to have been carried to Ireland from Holland in 1839, and is reported as existing in England in 1842. The disease was brought to the United States at several different times. Probably its first introduction was with a diseased cow sold in Brooklyn, N. Y., in 1843. It came to New Jersey by importing affected animals in 1847. Massachusetts was infected in the same way in 1859.

South Africa was infected by a bull brought from Holland in 1854, and Australia likewise received the contagion with an English cow in 1858. It is also reported as existing in various parts of the Continent of Asia, but the time of its first appearance and the extent of its distribution are very uncertain.

Some countries, such as Norway, Sweden, and Denmark, which had been infected for only a short time, have succeeded in eradicating the disease without much difficulty by slaughtering all affected and exposed animals. Other countries long infected and in which the contagion was thoroughly established, like Australia, South Africa, Italy, France, Belgium, and parts of Germany, have labored long, in some cases making no progress and in others being only partially successful. Holland was one of the first of the thoroughly infected countries to free itself from the contagion.

In the United States, Massachusetts eradicated pleuropneumonia during the period from 1860 to 1866. New York and New Jersey made an attempt to eradicate it in 1879, but were not successful. Late in 1883 the contagion was carried to Ohio, probably by Jersey cattle purchased in the vicinity of Baltimore, Md., to which place it had extended before 1868. From the herd then infected it was spread by the sale of cattle during 1884 to a limited number of herds in Illinois, to one herd in Missouri, and to two in Kentucky. The alarm caused among the stock owners of the United States by this widespread dissemination of a disease so much dreaded led to the adoption of active measures for its control and eradication. By cooperation between the United States Department of Agriculture and the authorities of the affected States it was found possible to prevent the further spread of the contagion and to eradicate it after a few months' delay.

In 1886 pleuropneumonia was discovered in some of the large distillery stables of Chicago and among cows on neighboring lots. This led to renewed efforts for the complete extirpation of this disease from the country. Congress in 1887 enlarged the appropriation available for this purpose and gave more extended authority. During the same year the disease was stamped out of Chicago, and has not since appeared in any district west of the Allegheny Mountains.

The work of eradication was at the same time commenced in all the infected States. Before the end of the year 1889 Pennsylvania, Delaware, Maryland, the District of Columbia, and Virginia had been freed from the disease. More difficulties, however, were encountered in the States of New York and New Jersey, on account of the larger territory infected and the density of the population. The long struggle was successful, however, and the last animal in which the disease appeared in the State of New York was slaughtered early in 1891, and the last one affected in New Jersey met the same fate early in the spring of 1892.









During these same years a supreme effort had been made to stamp out this lung plague from Great Britain. From the official reports it appears that the number of infected districts and of diseased animals had rapidly diminished, but it was not until 1898 that the infection was finally eradicated.

The other infected European countries, though they maintain a veterinary sanitary service, are not making satisfactory progress in eradicating the disease. This is owing partly to delays in carrying out the provisions of the laws and partly to mistaken ideas as to the measures which are necessary to accomplish the object. The United States was the last of the countries having old infected districts which undertook to stamp out this contagion, and, except Holland, it was the first to reach success.

The cause (etiology) of pleuropneumonia.—This is a contagious disease, and arises only by contagion from a previously affected animal; consequently it can never be seen here except as the result of importing affected animals from the Old World. When thoroughly stamped out it does not reappear; and if imported animals continue to be properly inspected and quarantined, we have every reason to believe that pleuropneumonia will never again be seen in this country.

The exact nature of the virus or contagion of lung plague has never been determined. Various investigators have from time to time claimed the discovery of the specific organism of the disease, but it was not until 1898 that Nocard and Roux, by an ingenious method of cultivation, succeeded in obtaining a very feeble growth of an exceedingly minute microorganism. With these cultures the disease was produced in cattle.

Some investigators and writers are of the opinion that the disease can be contracted only by an animal coming near enough to a living diseased one to receive the contagion directly from it. They hold that the contagion is expired with the air from the affected lungs, and that it must be almost immediately inspired by another animal in order to produce the disease. Some experimental attempts to infect animals by placing them in stables where diseased animals have been, and by placing the diseased lungs of slaughtered animals in their feeding troughs have failed, and, consequently, apparently confirm this view.

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CONTAGIOUS PLEUROPNEUMONIA. DESCRIPTION OF PLATES.

PLATE XXIX. Upper or dorsal surface of the lungs of the ox, reduced to one-twelfth of the natural size: a, a', the right and left principal lobes. These are the largest and are situated posteriorly, resting upon the diaphragm; b, b', the ventral lobes, situated between the principal lobes; and c, c', c'' the most anterior, or cephalic, lobes. The right anterior is divided into two lobes (c, c'), the left is single (c''); d, trachea, or windpipe.

In the majority of the lungs examined in the laboratory of the bureau which were affected with contagious pleuropneumonia the principal lobes (a, a') were primarily affected.

PLATE XXX. Bronchopneumonia. The ventral or middle lobe of the right lung affected with collapse and beginning bronchopneumonia. The light yellowish portions represent healthy lung tissue; the red represents the disease. It will be noticed that the lines between the lobules are quite faint, indicating little or no inflammation of the connective tissue between the lobules. The healthy lung tissue is seen to be raised above the level of the diseased portion. In contagious pleuropneumonia the exact reverse is the case, the diseased portions being very much larger than the healthy.