2. In the diseases occasioned by a defect of sensorial exertion, as in cold fits of ague, hysteric complaint, and nervous fever, the following means are those commonly used. 1. Increase the stimulation above its natural quantity for some weeks, till a new habit of more energetic contraction of the fibres is established. This is to be done by wine, opium, bark, steel, given at exact periods, and in appropriate quantities; for if these medicines be given in such quantity, as to induce the least degree of intoxication, a debility succeeds from the useless exhaustion of spirit of animation in consequence of too great exertion of the muscles or organs of sense. To these irritative stimuli should be added the sensitive ones of cheerful ideas, hope, affection.

3. Change the kinds of stimulus. The habits acquired by the constitution depend on such nice circumstances, that when one kind of stimulus ceases to excite the sensorial power into the quantity of exertion necessary to health, it is often sufficient to change the stimulus for another apparently similar in quantity and quality. Thus when wine ceases to stimulate the constitution, opium in appropriate doses supplies the defect; and the contrary. This is also observed in the effects of cathartic medicines, when one loses its power, another, apparently less efficacious, will succeed. Hence a change of diet, drink, and stimulating medicines, is often advantageous in diseases of debility.

4. Stimulate the organs, whose motions are associated with the torpid parts of the system. The actions of the minute vessels of the various parts of the external skin are not only associated with each other, but are strongly associated with those of some of the internal membranes, and particularly of the stomach. Hence when the exertion of the stomach is less than natural, and indigestion and heartburn succeed, nothing so certainly removes these symptoms as the stimulus of a blister on the back. The coldness of the extremities, as of the nose, ears, or fingers, are hence the best indication for the successful application of blisters.

5. Decrease the stimulus for a time. By lessening the quantity of heat for a minute or two by going into the cold bath, a great accumulation of sensorial power is produced; for not only the minute vessels of the whole external skin for a time become inactive, as appears by their paleness; but the minute vessels of the lungs lose much of their activity also by concert with those of the skin, as appears from the difficulty of breathing at first going into cold water. On emerging from the bath the sensorial power is thrown into great exertion by the stimulus of the common degree of the warmth of the atmosphere, and a great production of animal heat is the consequence. The longer a person continues in the cold bath the greater must be the present inertion of a great part of the system, and in consequence a greater accumulation of sensorial power. Whence M. Pome recommends some melancholy patients to be kept from two to six hours in spring-water, and in baths still colder.

6. Decrease the stimulus for a time below the natural, and then increase it above natural. The effect of this process, improperly used, is seen in giving much food, or applying much warmth, to those who have been previously exposed to great hunger, or to great cold. The accumulated sensorial power is thrown into so violent exertion, that inflammations and mortifications supervene, and death closes the catastrophe. In many diseases this method is the most successful; hence the bark in agues produces more certain effect after the previous exhibition of emetics. In diseases attended with violent pain, opium has double the effect, if venesection and a cathartic have been previously used. On this seems to have been founded the successful practice of Sydenham, who used venesection and a cathartic in chlorosis before the exhibition of the bark, steel, and opiates.

7. Prevent any unnecessary expenditure of sensorial power. Hence in fevers with debility, a decumbent posture is preferred, with silence, little light, and such a quantity of heat as may prevent any chill sensation, or any coldness of the extremities. The pulse of patients in fevers with debility increases in frequency above ten pulsations in a minute on their rising out of bed. For the expenditure of sensorial power to preserve an erect posture of the body adds to the general deficiency of it, and thus affects the circulation.

8. The longer in time and the greater in degree the quiescence or inertion of an organ has been, so that it still retains life or excitability, the less stimulus should at first be applied to it. The quantity of stimulation is a matter of great nicety to determine, where the torpor or quiescence of the fibres has been experienced in a great degree, or for a considerable time, as in cold fits of the ague, in continued fevers with great debility, or in people famished at sea, or perishing with cold. In the two last cases, very minute quantities of food should be first supplied, and very few additional degrees of heat. In the two former cases, but little stimulus of wine or medicine, above what they had been lately accustomed to, should be exhibited, and this at frequent and stated intervals, so that the effect of one quantity may be observed before the exhibition of another.

If these circumstances are not attended to, as the sensorial power becomes accumulated in the quiescent fibres, an inordinate exertion takes place by the increase of stimulus acting on the accumulated quantity of sensorial power, and either the paralysis, or death of the contractile fibres ensues, from the total expenditure of the sensorial power in the affected organ, owing to this increase of exertion, like the debility after intoxication. Or, secondly, the violent exertions above mentioned produce painful sensation, which becomes a new stimulus, and by thus producing inflammation, and increasing the activity of the fibres already too great, sooner exhausts the whole of the sensorial power in the acting organ, and mortification, that is, the death of the part, supervenes.

Hence there have been many instances of people, whose limbs have been long benumbed by exposure to cold, who have lost them by mortification on their being too hastily brought to the fire; and of others, who were nearly famished at sea, who have died soon after having taken not more than an usual meal of food. I have heard of two well-attested instances of patients in the cold fit of ague, who have died from the exhibition of gin and vinegar, by the inflammation which ensued. And in many fevers attended with debility, the unlimited use of wine, and the wanton application of blisters, I believe, has destroyed numbers by the debility consequent to too great stimulation, that is, by the exhaustion of the sensorial power by its inordinate exertion.

Wherever the least degree of intoxication exists, a proportional debility is the consequence; but there is a golden rule by which the necessary and useful quantity of stimulus in fevers with debility may be ascertained. When wine or beer are exhibited either alone or diluted with water, if the pulse becomes slower the stimulus is of a proper quantity; and should be repeated every two or three hours, or when the pulse again becomes quicker.

In the chronical debility brought on by drinking spirituous or fermented liquors, there is another golden rule by which I have successfully directed the quantity of spirit which they may safely lessen, for there is no other means by which they can recover their health. It should be premised, that where the power of digestion in these patients is totally destroyed, there is not much reason to expect a return to healthful vigour.

I have directed several of these patients to omit one fourth part of the quantity of vinous spirit they have been lately accustomed to, and if in a fortnight their appetite increases, they are advised to omit another fourth part; but if they perceive that their digestion becomes impaired from the want of this quantity of spirituous potation, they are advised to continue as they are, and rather bear the ills they have, than risk the encounter of greater. At the same time flesh-meat with or without spice is recommended, with Peruvian bark and steel in small quantities between their meals, and half a grain of opium or a grain, with five or eight grains of rhubarb at night.

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SECT. XIII.

OF VEGETABLE ANIMATION.

I. 1. Vegetables are irritable; mimosa, dionaea muscipula. Vegetable secretions. 2. Vegetable buds are inferior animals, are liable to greater or less irritability. II. Stamens and pistils of plants shew marks of sensibility. III. Vegetables possess some degree of volition. IV. Motions of plants are associated like those of animals. V. 1. Vegetable structure like that of animals, their anthers and stigmas are living creatures. Male-flowers of Vallisneria. 2. Whether vegetables, possess ideas? They have organs of sense as of touch and smell, and ideas of external things?

I. 1. The fibres of the vegetable world, as well as those of the animal, are excitable into a variety of motion by irritations of external objects. This appears particularly in the mimosa or sensitive plant, whose leaves contract on the slightest injury; the dionaea muscipula, which was lately brought over from the marshes of America, presents us with another curious instance of vegetable irritability; its leaves are armed with spines on their upper edge, and are spread on the ground around the stem; when an insect creeps on any of them in its passage to the flower or seed, the leaf shuts up like a steel rat-trap, and destroys its enemy. See Botanic Garden, Part II. note on Silene.

The various secretions of vegetables, as of odour, fruit, gum, resin, wax, honey, seem brought about in the same manner as in the glands of animals; the tasteless moisture of the earth is converted by the hop-plant into a bitter juice; as by the caterpillar in the nut-shell the sweet kernel is converted into a bitter powder. While the power of absorption in the roots and barks of vegetables is excited into action by the fluids applied to their mouths like the lacteals and lymphatics of animals.

2. The individuals of the vegetable world may be considered as inferior or less perfect animals; a tree is a congeries of many living buds, and in this respect resembles the branches of coralline, which are a congeries of a multitude of animals. Each of these buds of a tree has its proper leaves or petals for lungs, produces its viviparous or its oviparous offspring in buds or seeds; has its own roots, which extending down the stem of the tree are interwoven with the roots of the other buds, and form the bark, which is the only living part of the stem, is annually renewed, and is superinduced upon the former bark, which then dies, and with its stagnated juices gradually hardening into wood forms the concentric circles, which we see in blocks of timber.

The following circumstances evince the individuality of the buds of trees. First, there are many trees, whose whole internal wood is perished, and yet the branches are vegete and healthy. Secondly, the fibres of the barks of trees are chiefly longitudinal, resembling roots, as is beautifully seen in those prepared barks, that were lately brought from Otaheita. Thirdly, in horizontal wounds of the bark of trees, the fibres of the upper lip are always elongated downwards like roots, but those of the lower lip do not approach to meet them. Fourthly, if you wrap wet moss round any joint of a vine, or cover it with moist earth, roots will shoot out from it. Fifthly, by the inoculation or engrafting of trees many fruits are produced from one stem. Sixthly, a new tree is produced from a branch plucked from an old one, and set in the ground. Whence it appears that the buds of deciduous trees are so many annual plants, that the bark is a contexture of the roots of each individual bud; and that the internal wood is of no other use but to support them in the air, and that thus they resemble the animal world in their individuality.

The irritability of plants, like that of animals, appears liable to be increased or decreased by habit; for those trees or shrubs, which are brought from a colder climate to a warmer, put out their leaves and blossoms a fortnight sooner than the indigenous ones.

Professor Kalm, in his Travels in New York, observes that the apple-trees brought from England blossom a fortnight sooner than the native ones. In our country the shrubs, that are brought a degree or two from the north, are observed to flourish better than those, which come from the south. The Siberian barley and cabbage are said to grow larger in this climate than the similar more southern vegetables. And our hoards of roots, as of potatoes and onions, germinate with less heat in spring, after they have been accustomed to the winter's cold, than in autumn after the summer's heat.

II. The stamens and pistils of flowers shew evident marks of sensibility, not only from many of the stamens and some pistils approaching towards each other at the season of impregnation, but from many of them closing their petals and calyxes during the cold parts of the day. For this cannot be ascribed to irritation, because cold means a defect of the stimulus of heat; but as the want of accustomed stimuli produces pain, as in coldness, hunger, and thirst of animals, these motions of vegetables in closing up their flowers must be ascribed to the disgreeable sensation, and not to the irritation of cold. Others close up their leaves during darkness, which, like the former, cannot be owing to irritation, as the irritating material is withdrawn.

The approach of the anthers in many flowers to the stigmas, and of the pistils of some flowers to the anthers, must be ascribed to the passion of love, and hence belongs to sensation, not to irritation.

III. That the vegetable world possesses some degree of voluntary powers, appears from their necessity to sleep, which we have shewn in Sect. XVIII. to consist in the temporary abolition of voluntary power. This voluntary power seems to be exerted in the circular movement of the tendrils of vines, and other climbing vegetables; or in the efforts to turn the upper surface of their leaves, or their flowers to the light.

IV. The associations of fibrous motions are observable in the vegetable world, as well as in the animal. The divisions of the leaves of the sensitive plant have been accustomed to contract at the same time from the absence of light; hence if by any other circumstance, as a slight stroke or injury, one division is irritated into contraction, the neighbouring ones contract also, from their motions being associated with those of the irritated part. So the various stamina of the class of syngenesia have been accustomed to contract together in the evening, and thence if you stimulate one of them with a pin, according to the experiment of M. Colvolo, they all contract from their acquired associations.

To evince that the collapsing of the sensitive plant is not owing to any mechanical vibrations propagated along the whole branch, when a single leaf is struck with the finger, a leaf of it was slit with sharp scissors, and some seconds of time passed before the plant seemed sensible of the injury; and then the whole branch collapsed as far as the principal stem: this experiment was repeated several times with the least possible impulse to the plant.

V. 1. For the numerous circumstances in which vegetable buds are analogous to animals, the reader is referred to the additional notes at the end of the Botanic Garden, Part I. It is there shewn, that the roots of vegetables resemble the lacteal system of animals; the sap-vessels in the early spring, before their leaves expand, are analogous to the placental vessels of the foetus; that the leaves of land-plants resemble lungs, and those of aquatic plants the gills of fish; that there are other systems of vessels resembling the vena portarum of quadrupeds, or the aorta of fish; that the digestive power of vegetables is similar to that of animals converting the fluids, which they absorb, into sugar; that their seeds resemble the eggs of animals, and their buds and bulbs their viviparous offspring. And, lastly, that the anthers and stigmas are real animals, attached indeed to their parent tree like polypi or coral insects, but capable of spontaneous motion; that they are affected with the passion of love, and furnished with powers of reproducing their species, and are fed with honey like the moths and butterflies, which plunder their nectaries. See Botanic Garden, Part I. add. note XXXIX.

The male flowers of vallisneria approach still nearer to apparent animality, as they detach themselves from the parent plant, and float on the surface of the water to the female ones. Botanic Garden, Part II. Art. Vallisneria. Other flowers of the classes of monecia and diecia, and polygamia, discharge the fecundating farina, which floating in the air is carried to the stigma of the female flowers, and that at considerable distances. Can this be effected by any specific attraction? or, like the diffusion of the odorous particles of flowers, is it left to the currents of winds, and the accidental miscarriages of it counteracted by the quantity of its production?

2. This leads us to a curious enquiry, whether vegetables have ideas of external things? As all our ideas are originally received by our senses, the question may be changed to, whether vegetables possess any organs of sense? Certain it is, that they possess a sense of heat and cold, another of moisture and dryness, and another of light and darkness; for they close their petals occasionally from the presence of cold, moisture, or darkness. And it has been already shewn, that these actions cannot be performed simply from irritation, because cold and darkness are negative quantities, and on that account sensation or volition are implied, and in consequence a sensorium or union of their nerves. So when we go into the light, we contract the iris; not from any stimulus of the light on the fine muscles of the iris, but from its motions being associated with the sensation of too much light on the retina: which could not take place without a sensorium or center of union of the nerves of the iris with those of vision. See Botanic Garden, Part I. Canto 3. l. 440. note.

Besides these organs of sense, which distinguish cold, moisture, and darkness, the leaves of mimosa, and of dionaea, and of drosera, and the stamens of many flowers, as of the berbery, and the numerous class of syngenesia, are sensible to mechanic impact, that is, they possess a sense of touch, as well as a common sensorium; by the medium of which their muscles are excited into action. Lastly, in many flowers the anthers, when mature, approach the stigma, in others the female organ approaches to the male. In a plant of collinsonia, a branch of which is now before me, the two yellow stamens are about three eights of an inch high, and diverge from each other, at an angle of about fifteen degrees, the purple style is half an inch high, and in some flowers is now applied to the stamen on the right hand, and in others to that of the left; and will, I suppose, change place to-morrow in those, where the anthers have not yet effused their powder.

I ask, by what means are the anthers in many flowers, and stigmas in other flowers, directed to find their paramours? How do either of them know, that the other exists in their vicinity? Is this curious kind of storge produced by mechanic attraction, or by the sensation of love? The latter opinion is supported by the strongest analogy, because a reproduction of the species is the consequence; and then another organ of sense must be wanted to direct these vegetable amourettes to find each other, one probably analogous to our sense of smell, which in the animal world directs the new-born infant to its source of nourishment, and they may thus possess a faculty of perceiving as well as of producing odours.

Thus, besides a kind of taste at the extremities of their roots, similar to that of the extremities of our lacteal vessels, for the purpose of selecting their proper food: and besides different kinds of irritability residing in the various glands, which separate honey, wax, resin, and other juices from their blood; vegetable life seems to possess an organ of sense to distinguish the variations of heat, another to distinguish the varying degrees of moisture, another of light, another of touch, and probably another analogous to our sense of smell. To these must be added the indubitable evidence of their passion of love, and I think we may truly conclude, that they are furnished with a common sensorium belonging to each bud and that they must occasionally repeat those perceptions either in their dreams or waking hours, and consequently possess ideas of so many of the properties of the external world, and of their own existence.

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SECT. XIV.

OF THE PRODUCTION OF IDEAS.

I. Of material and immaterial beings. Doctrine of St. Paul. II. 1. Of the sense of touch. Of solidity. 2. Of figure. Motion. Time. Place. Space. Number. 3. Of the penetrability of matter. 4. Spirit of animation possesses solidity, figure, visibility, &c. Of Spirits and angels. 5. The existence of external things. III. Of vision. IV. Of hearing. V. Of smell and taste. VI. Of the organ of sense by which we perceive heat and cold, not by the sense of touch. VII. Of the sense of extension, the whole of the locomotive muscles may be considered as one organ of sense. VIII. Of the senses of hunger, thirst, want of fresh air, suckling children, and lust. IX. Of many other organs of sense belonging to the glands. Of painful sensations from the excess of light, pressure, heat, itching, caustics, and electricity.

I. Philosophers have been much perplexed to understand, in what manner we become acquainted with the external world; insomuch that Dr. Berkly even doubted its existence, from having observed (as he thought) that none of our ideas resemble their correspondent objects. Mr. Hume asserts, that our belief depends on the greater distinctness or energy of our ideas from perception; and Mr. Reid has lately contended, that our belief of external objects is an innate principle necessarily joined with our perceptions.

So true is the observation of the famous Malbranch, "that our senses are not given us to discover the essences of things, but to acquaint us with the means of preserving our existence," (L. I. ch. v.) a melancholy reflection to philosophers!

Some philosophers have divided all created beings into material and immaterial: the former including all that part of being, which obeys the mechanic laws of action and reaction, but which can begin no motion of itself; the other is the cause of all motion, and is either termed the power of gravity, or of specific attraction, or the spirit of animation. This immaterial agent is supposed to exist in or with matter, but to be quite distinct from it, and to be equally capable of existence, after the matter, which now possesses it, is decomposed.

Nor is this theory ill supported by analogy, since heat, electricity, and magnetism, can be given to or taken from a piece of iron; and must therefore exist, whether separated from the metal, or combined with it. From a parity of reasoning, the spirit of animation, would appear to be capable of existing as well separately from the body as with it.

I beg to be understood, that I do not wish to dispute about words, and am ready to allow, that the powers of gravity, specific attraction, electricity, magnetism, and even the spirit of animation, may consist of matter of a finer kind; and to believe, with St. Paul and Malbranch, that the ultimate cause only of all motion is immaterial, that is God. St. Paul says, "in him we live and move, and have our being;" and, in the 15th chapter to the Corinthians, distinguishes between the psyche or living spirit, and the pneuma or reviving spirit. By the words spirit of animation or sensorial power, I mean only that animal life, which mankind possesses in common with brutes, and in some degree even with vegetables, and leave the consideration of the immortal part of us, which is the object of religion, to those who treat of revelation.

II. 1. Of the Sense of Touch.

The first idea we become acquainted with, are those of the sense of touch; for the foetus must experience some varieties of agitation, and exert some muscular action, in the womb; and may with great probability be supposed thus to gain some ideas of its own figure, of that of the uterus, and of the tenacity of the fluid, that surrounds it, (as appears from the facts mentioned in the succeeding Section upon Instinct.)

Many of the organs of sense are confined to a small part of the body, as the nostrils, ear, or eye, whilst the sense of touch is diffused over the whole skin, but exists with a more exquisite degree of delicacy at the extremities of the fingers and thumbs, and in the lips. The sense of touch is thus very commodiously disposed for the purpose of encompassing smaller bodies, and for adapting itself to the inequalities of larger ones. The figure of small bodies seems to be learnt by children by their lips as much as by their fingers; on which account they put every new object to their mouths, when they are satiated with food, as well as when they are hungry. And puppies seem to learn their ideas of figure principally by the lips in their mode of play.

We acquire our tangible ideas of objects either by the simple pressure of this organ of touch against a solid body, or by moving our organ of touch along the surface of it. In the former case we learn the length and breadth of the object by the quantity of our organ of touch, that is impressed by it: in the latter case we learn the length and breadth of objects by the continuance of their pressure on our moving organ of touch.

It is hence, that we are very slow in acquiring our tangible ideas, and very slow in recollecting them; for if I now think of the tangible idea of a cube, that is, if I think of its figure, and of the solidity of every part of that figure, I must conceive myself as passing my fingers over it, and seem in some measure to feel the idea, as I formerly did the impression, at the ends of them, and am thus very slow in distinctly recollecting it.

When a body compresses any part of our sense of touch, what happens? First, this part of our sensorium undergoes a mechanical compression, which is termed a stimulus; secondly, an idea, or contraction of a part of the organ of sense is excited; thirdly, a motion of the central parts, or of the whole sensorium, which is termed sensation, is produced; and these three constitute the perception of solidity.

2. Of Figure, Motion, Time, Place, Space, Number.

No one will deny, that the medulla of the brain and nerves has a certain figure; which, as it is diffused through nearly the whole of the body, must have nearly the figure of that body. Now it follows, that the spirit of animation, or living principle, as it occupies this medulla, and no other part, (which is evinced by a great variety of cruel experiments on living animals,) it follows, that this spirit of animation has also the same figure as the medulla above described. I appeal to common sense! the spirit of animation acts, Where does it act? It acts wherever there is the medulla above mentioned; and that whether the limb is yet joined to a living animal, or whether it be recently detached from it; as the heart of a viper or frog will renew its contractions, when pricked with a pin, for many minutes of time after its exsection from the body.—Does it act any where else?—No; then it certainly exists in this part of space, and no where else; that is, it hath figure; namely, the figure of the nervous system, which is nearly the figure of the body. When the idea of solidity is excited, as above explained, a part of the extensive organ of touch is compressed by some external body, and this part of the sensorium so compressed exactly resembles in figure the figure of the body that compressed it. Hence, when we acquire the idea of solidity, we acquire at the same time the idea of FIGURE; and this idea of figure, or motion of a part of the organ of touch, exactly resembles in its figure the figure of the body that occasions it; and thus exactly acquaints us with this property of the external world.

Now, as the whole universe with all its parts possesses a certain form or figure, if any part of it moves, that form or figure of the whole is varied: hence, as MOTION is no other than a perpetual variation of figure, our idea of motion is also a real resemblance of the motion that produced it.

It may be said in objection to this definition of motion, that an ivory globe may revolve on its axis, and that here will be a motion without change of figure. But the figure of the particle x on one side of this globe is not the same figure as the figure of y on the other side, any more than the particles themselves are the same, though they are similar figures; and hence they cannot change place with each other without disturbing or changing the figure of the whole.

Our idea of TIME is from the same source, but is more abstracted, as it includes only the comparative velocities of these variations of figure; hence if it be asked, How long was this book in printing? it may be answered, Whilst the sun was passing through Aries.

Our idea of PLACE includes only the figure of a group of bodies, not the figures of the bodies themselves. If it be asked where is Nottinghamshire, the answer is, it is surrounded by Derbyshire, Lincolnshire and Leicestershire; hence place is our idea of the figure of one body surrounded by the figures of other bodies.

The idea of SPACE is a more abstracted idea of place excluding the group of bodies.

The idea of NUMBER includes only the particular arrangements, or distributions of a group of bodies, and is therefore only a more abstracted idea of the parts of the figure of the group of bodies; thus when I say England is divided into forty counties, I only speak of certain divisions of its figure.

Hence arises the certainty of the mathematical sciences, as they explain these properties of bodies, which are exactly resembled by our ideas of them, whilst we are obliged to collect almost all our other knowledge from experiment; that is, by observing the effects exerted by one body upon another.

3. Of the Penetrability of Matter.

The impossibility of two bodies existing together in the same space cannot be deduced from our idea of solidity, or of figure. As soon as we perceive the motions of objects that surround us, and learn that we possess a power to move our own bodies, we experience, that those objects, which excite in us the idea of solidity and of figure, oppose this voluntary movement of our own organs; as whilst I endeavour to compress between my hands an ivory ball into a spheroid. And we are hence taught by experience, that our own body and those, which we touch, cannot exist in the same part of space.

But this by no means demonstrates, that no two bodies can exist together in the same part of space. Galilaeo in the preface to his works seems to be of opinion, that matter is not impenetrable; Mr. Michel, and Mr. Boscowich in his Theoria. Philos. Natur. have espoused this hypothesis: which has been lately published by Dr. Priestley, to whom the world is much indebted for so many important discoveries in science. (Hist. of Light and Colours, p. 391.) The uninterrupted passage of light through transparent bodies, of the electric aether through metallic and aqueous bodies, and of the magnetic effluvia through all bodies, would seem to give some probability to this opinion. Hence it appears, that beings may exist without possessing the property of solidity, as well as they can exist without possessing the properties, which excite our smell or taste, and can thence occupy space without detruding other bodies from it; but we cannot become acquainted with such beings by our sense of touch, any more than we can with odours or flavours without our senses of smell and taste.

But that any being can exist without existing in space, is to my ideas utterly incomprehensible. My appeal is to common sense. To be implies a when and a where; the one is comparing it with the motions of other beings, and the other with their situations.

If there was but one object, as the whole creation may be considered as one object, then I cannot ask where it exists? for there are no other objects to compare its situation with. Hence if any one denies, that a being exists in space, he denies, that there are any other beings but that one; for to answer the question, "Where does it exist?" is only to mention the situation of the objects that surround it.

In the same manner if it be asked—"When does a being exist?" The answer only specifies the successive motions either of itself, or of other bodies; hence to say, a body exists not in time, is to say, that there is, or was, no motion in the world.

4. Of the Spirit of Animation.

But though there may exist beings in the universe, that have not the property of solidity; that is, which can possess any part of space, at the same time that it is occupied by other bodies; yet there may be other beings, that can assume this property of solidity, or disrobe themselves of it occasionally, as we are taught of spirits, and of angels; and it would seem, that THE SPIRIT OF ANIMATION must be endued with this property, otherwise how could it occasionally give motion to the limbs of animals?—or be itself stimulated into motion by the obtrusions of surrounding bodies, as of light, or odour?

If the spirit of animation was always necessarily penetrable, it could not influence or be influenced by the solidity of common matter; they would exist together, but could not detrude each other from the part of space, where they exist; that is, they could not communicate motion to each other. No two things can influence or affect each other, which have not some property common to both of them; for to influence or affect another body is to give or communicate some property to it, that it had not before; but how can one body give that to another, which it does not possess itself?—The words imply, that they must agree in having the power or faculty of possessing some common property. Thus if one body removes another from the part of space, that it possesses, it must have the power of occupying that space itself: and if one body communicates heat or motion to another, it follows, that they have alike the property of possessing heat or motion.

Hence the spirit of animation at the time it communicates or receives motion from solid bodies, must itself possess some property of solidity. And in consequence at the time it receives other kinds of motion from light, it must possess that property, which light possesses, to communicate that kind of motion; and for which no language has a name, unless it may be termed Visibility. And at the time it is stimulated into other kinds of animal motion by the particles of sapid and odorous bodies affecting the senses of taste and smell, it must resemble these particles of flavour, and of odour, in possessing some similar or correspondent property; and for which language has no name, unless we may use the words Saporosity and Odorosity for those common properties, which are possessed by our organs of taste and smell, and by the particles of sapid and odorous bodies; as the words Tangibility and Audibility may express the common property possessed by our organs of touch, and of hearing, and by the solid bodies, or their vibrations, which affect those organs.

5. Finally, though the figures of bodies are in truth resembled by the figure of the part of the organ of touch, which is stimulated into motion; and that organ resembles the solid body, which stimulates it, in its property of solidity; and though the sense of hearing resembles the vibrations of external bodies in its capability of being stimulated into motion by those vibrations; and though our other organs of sense resemble the bodies, that stimulate them, in their capability of being stimulated by them; and we hence become acquainted with these properties of the external world; yet as we can repeat all these motions of our organs of sense by the efforts of volition, or in consequence of the sensation of pleasure or pain, or by their association with other fibrous motions, as happens in our reveries or in sleep, there would still appear to be some difficulty in demonstrating the existence of any thing external to us.

In our dreams we cannot determine this circumstance, because our power of volition is suspended, and the stimuli of external objects are excluded; but in our waking hours we can compare our ideas belonging to one sense with those belonging to another, and can thus distinguish the ideas occasioned by irritation from those excited by sensation, volition, or association. Thus if the idea of the sweetness of sugar should be excited in our dreams, the whiteness and hardness of it occur at the same time by association; and we believe a material lump of sugar present before us. But if, in our waking hours, the idea of the sweetness of sugar occurs to us, the stimuli of surrounding objects, as the edge of the table, on which we press, or green colour of the grass, on which we tread, prevent the other ideas of the hardness and whiteness of the sugar from being exerted by association. Or if they should occur, we voluntarily compare them with the irritative ideas of the table or grass above mentioned, and detect their fallacy. We can thus distinguish the ideas caused by the stimuli of external objects from those, which are introduced by association, sensation, or volition; and during our waking hours can thus acquire a knowledge of the external world. Which nevertheless we cannot do in our dreams, because we have neither perceptions of external bodies, nor the power of volition to enable us to compare them with the ideas of imagination.

III. Of Vision.

Our eyes observe a difference of colour, or of shade, in the prominences and depressions of objects, and that those shades uniformly vary, when the sense of touch observes any variation. Hence when the retina becomes stimulated by colours or shades of light in a certain form, as in a circular spot; we know by experience, that this is a sign, that a tangible body is before us; and that its figure is resembled by the miniature figure of the part of the organ of vision, that is thus stimulated.

Here whilst the stimulated part of the retina resembles exactly the visible figure of the whole in miniature, the various kinds of stimuli from different colours mark the visible figures of the minuter parts; and by habit we instantly recall the tangible figures.

Thus when a tree is the object of sight, a part of the retina resembling a flat branching figure is stimulated by various shades of colours; but it is by suggestion, that the gibbosity of the tree, and the moss, that fringes its trunk, appear before us. These are ideas of suggestion, which we feel or attend to, associated with the motions of the retina, or irritative ideas, which we do not attend to.

So that though our visible ideas resemble in miniature the outline of the figure of coloured bodies, in other respects they serve only as a language, which by acquired associations introduce the tangible ideas of bodies. Hence it is, that this sense is so readily deceived by the art of the painter to our amusement and instruction. The reader will find much very curious knowledge on this subject in Bishop Berkley's Essay on Vision, a work of great ingenuity.

The immediate object however of the sense of vision is light; this fluid, though its velocity is so great, appears to have no perceptible mechanical impulse, as was mentioned in the third Section, but seems to stimulate the retina into animal motion by its transmission through this part of the sensorium: for though the eyes of cats or other animals appear luminous in obscure places; yet it is probable, that none of the light, which falls on the retina, is reflected from it, but adheres to or enters into combination with the choroide coat behind it.

The combination of the particles of light with opake bodies, and therefore with the choroide coat of the eye, is evinced from the heat, which is given out, as in other chemical combinations. For the sunbeams communicate no heat in their passage through transparent bodies, with which they do not combine, as the air continues cool even in the focus of the largest burning-glasses, which in a moment vitrifies a particle of opaque matter.

IV. Of the Organ of Hearing.

It is generally believed, that the tympanum of the ear vibrates mechanically, when exposed to audible sounds, like the strings of one musical instrument, when the same notes are struck upon another. Nor is this opinion improbable, as the muscles and cartilages of the larynx are employed in producing variety of tones by mechanical vibration: so the muscles and bones of the ear seem adapted to increase or diminish the tension of the tympanum for the purposes of similar mechanical vibrations.

But it appears from dissection, that the tympanum is not the immediate organ of hearing, but that like the humours and cornea of the eye, it is only of use to prepare the object for the immediate organ. For the portio mollis of the auditory nerve is not spread upon the tympanum, but upon the vestibulum, and cochlea, and semicircular canals of the ear; while between the tympanum and the expansion of the auditory nerve the cavity is said by Dr. Cotunnus and Dr. Meckel to be filled with water; as they had frequently observed by freezing the heads of dead animals before they dissected them; and water being a more dense fluid than air is much better adapted to the propagation of vibrations. We may add, that even the external opening of the ear is not absolutely necessary for the perception of sound: for some people, who from these defects would have been completely deaf, have distinguished acute or grave sounds by the tremours of a stick held between their teeth propagated along the bones of the head, (Haller. Phys. T. V. p. 295).

Hence it appears, that the immediate organ of hearing is not affected by the particles of the air themselves, but is stimulated into animal motion by the vibrations of them. And it is probable from the loose bones, which are found in the heads of some fishes, that the vibrations of water are sensible to the inhabitants of that element by a similar organ.

The motions of the atmosphere, which we become acquainted with by the sense of touch, are combined with its solidity, weight, or vis intertiae; whereas those, that are perceived by this organ, depend alone on its elasticity. But though the vibration of the air is the immediate object of the sense of hearing, yet the ideas, we receive by this sense, like those received from light, are only as a language, which by acquired associations acquaints us with those motions of tangible bodies, which depend on their elasticity; and which we had before learned by our sense of touch.

V. Of Smell and of Taste.

The objects of smell are dissolved in the fluid atmosphere, and those of taste in the saliva, or other aqueous fluid, for the better diffusing them on their respective organs, which seem to be stimulated into animal motion perhaps by the chemical affinities of these particles, which constitute the sapidity and odorosity of bodies with the nerves of sense, which perceive them.

Mr. Volta has lately observed a curious circumstance relative to our sense of taste. If a bit of clean lead and a bit of clean silver be separately applied to the tongue and palate no taste is perceived; but by applying them in contact in respect to the parts out of the mouth, and nearly so in respect to the parts, which are immediately applied to the tongue and palate, a saline or acidulous taste is perceived, as of a fluid like a stream of electricity passing from one of them to the other. This new application of the sense of taste deserves further investigation, as it may acquaint us with new properties of matter.

From the experiments above mentioned of Galvani, Volta, Fowler, and others, it appears, that a plate of zinc and a plate of silver have greater effect than lead and silver. If one edge of a plate of silver about the size of half a crown-piece be placed upon the tongue, and one edge of a plate of zinc about the same size beneath the tongue, and if their opposite edges are then brought into contact before the point of the tongue, a taste is perceived at the moment of their coming into contact; secondly, if one of the above plates be put between the upper lip and the gum of the fore-teeth, and the other be placed under the tongue, and their exterior edges be then brought into contact in a darkish room, a flash of light is perceived in the eyes.

These effects I imagine only shew the sensibility of our nerves of sense to very small quantities of the electric fluid, as it passes through them; for I suppose these sensations are occasioned by slight electric shocks produced in the following manner. By the experiments published by Mr. Bennet, with his ingenious doubler of electricity, which is the greatest discovery made in that science since the coated jar, and the eduction of lightning from the skies, it appears that zinc was always found minus, and silver was always found plus, when both of them were in their separate state. Hence, when they are placed in the manner above described, as soon as their exterior edges come nearly into contact, so near as to have an extremely thin plate of air between them, that plate of air becomes charged in the same manner as a plate of coated glass; and is at the same instant discharged through the nerves of taste or of sight, and gives the sensations, as above described, of light or of saporocity; and only shews the great sensibility of these organs of sense to the stimulus of the electric fluid in suddenly passing through them.

VI. Of the Sense of Heat.

There are many experiments in chemical writers, that evince the existence of heat as a fluid element, which covers and pervades all bodies, and is attracted by the solutions of some of them, and is detruded from the combination of others. Thus from the combinations of metals with acids, and from those combinations of animal fluids, which are termed secretions, this fluid matter of heat is given out amongst the neighbouring bodies; and in the solutions of salts in water, or of water in air, it is absorbed from the bodies, that surround them; whilst in its facility in passing through metallic bodies, and its difficulty in pervading resins and glass, it resembles the properties of the electric aura; and is like that excited by friction, and seems like that to gravitate amongst other bodies in its uncombined state, and to find its equilibrium.

There is no circumstance of more consequence in the animal economy than a due proportion of this fluid of heat; for the digestion of our nutriment in the stomach and bowels, and the proper qualities of all our secreted fluids, as they are produced or prepared partly by animal and partly by chemical processes, depend much on the quantity of heat; the excess of which, or its deficiency, alike gives us pain, and induces us to avoid the circumstances that occasion them. And in this the perception of heat essentially differs from the perceptions of the sense of touch, as we receive pain from too great pressure of solid bodies, but none from the absence of it. It is hence probable, that nature has provided us with a set of nerves for the perception of this fluid, which anatomists have not yet attended to.

There may be some difficulty in the proof of this assertion; if we look at a hot fire, we experience no pain of the optic nerve, though the heat along with the light must be concentrated upon it. Nor does warm water or warm oil poured into the ear give pain to the organ of hearing; and hence as these organs of sense do not perceive small excesses or deficiences of heat; and as heat has no greater analogy to the solidity or to the figures of bodies, than it has to their colours or vibrations; there seems no sufficient reason for our ascribing the perception of heat and cold to the sense of touch; to which it has generally been attributed, either because it is diffused beneath the whole skin like the sense of touch, or owing to the inaccuracy of our observations, or the defect of our languages.

There is another circumstance would induce us to believe, that the perceptions of heat and cold do not belong to the organ of touch; since the teeth, which are the least adapted for the perceptions of solidity or figure, are the most sensible to heat or cold; whence we are forewarned from swallowing those materials, whose degree of coldness or of heat would injure our stomachs.

The following is an extract from a letter of Dr. R.W. Darwin, of Shrewsbury, when he was a student at Edinburgh. "I made an experiment yesterday in our hospital, which much favours your opinion, that the sensation of heat and of touch depend on different sets of nerves. A man who had lately recovered from a fever, and was still weak, was seized with violent cramps in his legs and feet; which were removed by opiates, except that one of his feet remained insensible. Mr. Ewart pricked him with a pin in five or six places, and the patient declared he did not feel it in the least, nor was he sensible of a very smart pinch. I then held a red-hot poker at some distance, and brought it gradually nearer till it came within three inches, when he asserted that he felt it quite distinctly. I suppose some violent irritation on the nerves of touch had caused the cramps, and had left them paralytic; while the nerves of heat, having suffered no increased stimulus, retained their irritability."

Add to this, that the lungs, though easily stimulated into inflammation, are not sensible to heat. See Class. III. 1. 1. 10.

VII. Of the Sense of Extension.

The organ of touch is properly the sense of pressure, but the muscular fibres themselves constitute the organ of sense, that feels extension. The sense of pressure is always attended with the ideas of the figure and solidity of the object, neither of which accompany our perception of extension. The whole set of muscles, whether they are hollow ones, as the heart, arteries, and intestines, or longitudinal ones attached to bones, contract themselves, whenever they are stimulated by forcible elongation; and it is observable, that the white muscles, which constitute the arterial system, seem to be excited into contraction from no other kinds of stimulus, according to the experiments of Haller. And hence the violent pain in some inflammations, as in the paronychia, obtains immediate relief by cutting the membrane, that was stretched by the tumour of the subjacent parts.

Hence the whole muscular system may be considered as one organ of sense, and the various attitudes of the body, as ideas belonging to this organ, of many of which we are hourly conscious, while many others, like the irritative ideas of the other senses, are performed without our attention.

When the muscles of the heart cease to act, the refluent blood again distends or elongates them; and thus irritated they contract as before. The same happens to the arterial system, and I suppose to the capillaries, intestines, and various glands of the body.

When the quantity of urine, or of excrement, distends the bladder, or rectum, those parts contract, and exclude their contents, and many other muscles by association act along with them; but if these evacuations are not soon complied with, pain is produced by a little further extension of the muscular fibres: a similar pain is caused in the muscles, when a limb is much extended for the reduction of dislocated bones; and in the punishment of the rack: and in the painful cramps of the calf of the leg, or of other muscles, for a greater degree of contraction of a muscle, than the movement of the two bones, to which its ends are affixed, will admit of, must give similar pain to that, which is produced by extending it beyond its due length. And the pain from punctures or incisions arises from the distention of the fibres, as the knife passes through them; for it nearly ceases as soon as the division is completed.

All these motions of the muscles, that are thus naturally excited by the stimulus of distending bodies, are also liable to be called into strong action by their catenation, with the irritations or sensations produced by the momentum of the progressive particles of blood in the arteries, as in inflammatory fevers, or by acrid substances on other sensible organs, as in the strangury, or tenesmus, or cholera.

We shall conclude this account of the sense of extension by observing, that the want of its object is attended with a disagreeable sensation, as well as the excess of it. In those hollow muscles, which have been accustomed to it, this disagreeable sensation is called faintness, emptiness, and sinking; and, when it arises to a certain degree, is attended with syncope, or a total quiescence of all motions, but the internal irritative ones, as happens from sudden loss of blood, or in the operation of tapping in the dropsy.

VIII. Of the Appetites of Hunger, Thirst, Heat, Extension, the want of fresh Air, animal Love, and the Suckling of Children.

Hunger is most probably perceived by those numerous ramifications of nerves that are seen about the upper opening of the stomach; and thirst by the nerves about the fauces, and the top of the gula. The ideas of these senses are few in the generality of mankind, but are more numerous in those, who by disease, or indulgence, desire particular kinds of foods or liquids.

A sense of heat has already been spoken of, which may with propriety be called an appetite, as we painfully desire it, when it is deficient in quantity.

The sense of extension may be ranked amongst these appetites, since the deficiency of its object gives disagreeable sensation; when this happens in the arterial system, it is called faintness, and seems to bear some analogy to hunger and to cold; which like it are attended with emptiness of a part of the vascular system.

The sense of want of fresh air has not been attended to, but is as distinct as the others, and the first perhaps that we experience after our nativity; from the want of the object of this sense many diseases are produced, as the jail-fever, plague, and other epidemic maladies. Animal love is another appetite, which occurs later in life, and the females of lactiferous animals have another natural inlet of pleasure or pain from the suckling their offspring. The want of which either owing to the death of their progeny, or to the fashion of their country, has been fatal to many of the sex. The males have also pectoral glands, which are frequently turgid with a thin milk at their nativity, and are furnished with nipples, which erect on titillation like those of the female; but which seem now to be of no further use, owing perhaps to some change which these animals have undergone in the gradual progression of the formation of the earth, and of all that it inhabit.

These seven last mentioned senses may properly be termed appetites, as they differ from those of touch, sight, hearing, taste, and smell, in this respect; that they are affected with pain as well by the defect of their objects as by the excess of them, which is not so in the latter. Thus cold and hunger give us pain, as well as an excess of heat or satiety; but it is not so with darkness and silence.

IX. Before we conclude this Section on the organs of sense, we must observe, that, as far as we know, there are many more senses, than have been here mentioned, as every gland seems to be influenced to separate from the blood, or to absorb from the cavities of the body, or from the atmosphere, its appropriated fluid, by the stimulus of that fluid on the living gland; and not by mechanical capillary absorption, nor by chemical affinity. Hence it appears, that each of these glands must have a peculiar organ to perceive these irritations, but as these irritations are not succeeded by sensation, they have not acquired the names of senses.

However when these glands are excited into motions stronger than usual, either by the acrimony of their fluids, or by their own irritability being much increased, then the sensation of pain is produced in them as in all the other senses of the body; and these pains are all of different kinds, and hence the glands at this time really become each a different organ of sense, though these different kinds of pain have acquired no names.

Thus a great excess of light does not give the idea of light but of pain; as in forcibly opening the eye when it is much inflamed. The great excess of pressure or distention, as when the point of a pin is pressed upon our skin, produces pain, (and when this pain of the sense of distention is slighter, it is termed itching, or tickling), without any idea of solidity or of figure: an excess of heat produces smarting, of cold another kind of pain; it is probable by this sense of heat the pain produced by caustic bodies is perceived, and of electricity, as all these are fluids, that permeate, distend, or decompose the parts that feel them.

* * * * *

SECT. XV.

OF THE CLASSES OF IDEAS.

I. 1. Ideas received in tribes. 2. We combine them further, or abstract from these tribes. 3. Complex ideas. 4. Compounded ideas. 5. Simple ideas, modes, substances, relations, general ideas. 6. Ideas of reflexion. 7. Memory and imagination imperfectly defined. Ideal presence. Memorandum-rings. II. 1. Irritative ideas. Perception. 2. Sensitive ideas, imagination. 3. Voluntary ideas, recollection. 4. Associated ideas, suggestion. III. 1. Definitions of perception, memory. 2. Reasoning, judgment, doubting, distinguishing, comparing. 3. Invention. 4. Consciousness. 5. Identity. 6. Lapse of time. 7. Free-will.

I. 1. As the constituent elements of the material world are only perceptible to our organs of sense in a state of combination; it follows, that the ideas or sensual motions excited by them, are never received singly, but ever with a greater or less degree of combination. So the colours of bodies or their hardnesses occur with their figures: every smell and taste has its degree of pungency as well as its peculiar flavour: and each note in music is combined with the tone of some instrument. It appears from hence, that we can be sensible of a number of ideas at the same time, such as the whiteness, hardness, and coldness, of a snow-ball, and can experience at the same time many irritative ideas of surrounding bodies, which we do not attend to, as mentioned in Section VII. 3. 2. But those ideas which belong to the same sense, seem to be more easily combined into synchronous tribes, than those which were not received by the same sense, as we can more easily think of the whiteness and figure of a lump of sugar at the same time, than the whiteness and sweetness of it.

2. As these ideas, or sensual motions, are thus excited with greater or less degrees of combination; so we have a power, when we repeat them either by our volition or sensation, to increase or diminish this degree of combination, that is, to form compounded ideas from those, which were more simple; and abstract ones from those, which were more complex, when they were first excited; that is, we can repeat a part or the whole of those sensual motions, which did constitute our ideas of perception; and the repetition of which now constitutes our ideas of recollection, or of imagination.

3. Those ideas, which we repeat without change of the quantity of that combination, with which we first received them, are called complex ideas, as when you recollect Westminster Abbey, or the planet Saturn: but it must be observed, that these complex ideas, thus re-excited by volition, sensation, or association, are seldom perfect copies of their correspondent perceptions, except in our dreams, where other external objects do not detract our attention.

4. Those ideas, which are more complex than the natural objects that first excited them, have been called compounded ideas, as when we think of a sphinx, or griffin.

5. And those that are less complex than the correspondent natural objects, have been termed abstracted ideas: thus sweetness, and whiteness, and solidity, are received at the same time from a lump of sugar, yet I can recollect any of these qualities without thinking of the others, that were excited along with them.

When ideas are so far abstracted as in the above example, they have been termed simple by the writers of metaphysics, and seem indeed to be more complete repetitions of the ideas or sensual motions, originally excited by external objects.

Other classes of these ideas, where the abstraction has not been so great, have been termed, by Mr. Locke, modes, substances, and relations, but they seem only to differ in their degree of abstraction from the complex ideas that were at first excited; for as these complex or natural ideas are themselves imperfect copies of their correspondent perceptions, so these abstract or general ideas are only still more imperfect copies of the same perceptions. Thus when I have seen an object but once, as a rhinoceros, my abstract idea of this animal is the same as my complex one. I may think more or less distinctly of a rhinoceros, but it is the very rhinoceros that I saw, or some part or property of him, which recurs to my mind.

But when any class of complex objects becomes the subject of conversation, of which I have seen many individuals, as a castle or an army, some property or circumstance belonging to it is peculiarly alluded to; and then I feel in my own mind, that my abstract idea of this complex object is only an idea of that part, property, or attitude of it, that employs the present conversation, and varies with every sentence that is spoken concerning it. So if any one should say, "one may sit upon a horse safer than on a camel," my abstract idea of the two animals includes only an outline of the level back of the one, and the gibbosity on the back of the other. What noise is that in the street?—Some horses trotting over the pavement. Here my idea of the horses includes principally the shape and motion of their legs. So also the abstract ideas of goodness and courage are still more imperfect representations of the objects they were received from; for here we abstract the material parts, and recollect only the qualities.

Thus we abstract so much from some of our complex ideas, that at length it becomes difficult to determine of what perception they partake; and in many instances our idea seems to be no other than of the sound or letters of the word, that stands for the collective tribe, of which we are said to have an abstracted idea, as noun, verb, chimaera, apparition.

6. Ideas have been divided into those of perception and those of reflection, but as whatever is perceived must be external to the organ that perceives it, all our ideas must originally be ideas of perception.

7. Others have divided our ideas into those of memory, and those of imagination; they have said that a recollection of ideas in the order they were received constitutes memory, and without that order imagination; but all the ideas of imagination, excepting the few that are termed simple ideas, are parts of trains or tribes in the order they were received; as if I think of a sphinx, or a griffin, the fair face, bosom, wings, claws, tail, are all complex ideas in the order they were received: and it behoves the writers, who adhere to this definition, to determine, how small the trains must be, that shall be called imagination; and how great those, that shall be called memory.

Others have thought that the ideas of memory have a greater vivacity than those of imagination: but the ideas of a person in sleep, or in a waking reverie, where the trains connected with sensation are uninterrupted, are more vivid and distinct than those of memory, so that they cannot be distinguished by this criterion.

The very ingenious author of the Elements of Criticism has described what he conceives to be a species of memory, and calls it ideal presence; but the instances he produces are the reveries of sensation, and are therefore in truth connections of the imagination, though they are recalled in the order they were received.

The ideas connected by association are in common discourse attributed to memory, as we talk of memorandum-rings, and tie a knot on our handkerchiefs to bring something into our minds at a distance of time. And a school-boy, who can repeat a thousand unmeaning lines in Lilly's Grammar, is said to have a good memory. But these have been already shewn to belong to the class of association; and are termed ideas of suggestion.

II. Lastly, the method already explained of classing ideas into those excited by irritation, sensation, volition, or association, we hope will be found more convenient both for explaining the operations of the mind, and for comparing them with those of the body; and for the illustration and the cure of the diseases of both, and which we shall here recapitulate.

1. Irritative ideas are those, which are preceded by irritation, which is excited by objects external to the organs of sense: as the idea of that tree, which either I attend to, or which I shun in walking near it without attention. In the former case it is termed perception, in the latter it is termed simply an irritative idea.

2. Sensitive ideas are those, which are preceded by the sensation of pleasure or pain; as the ideas, which constitute our dreams or reveries, this is called imagination.

3. Voluntary ideas are those, which are preceded by voluntary exertion, as when I repeat the alphabet backwards: this is called recollection.

4. Associate ideas are those, which are preceded by other ideas or muscular motions, as when we think over or repeat the alphabet by rote in its usual order; or sing a tune we are accustomed to; this is called suggestion.

III. 1. Perceptions signify those ideas, which are preceded by irritation and succeeded by the sensation of pleasure or pain, for whatever excites our attention interests us; that is, it is accompanied with, pleasure or pain; however slight may be the degree or quantity of either of them.

The word memory includes two classes of ideas, either those which, are preceded by voluntary exertion, or those which are suggested by their associations with other ideas.

2. Reasoning is that operation of the sensorium, by which we excite two or many tribes of ideas; and then re-excite the ideas, in which they differ, or correspond. If we determine this difference, it is called judgment; if we in vain endeavour to determine it, it is called doubting.

If we re-excited the ideas, in which they differ, it is called distinguishing. If we re-excite those in which they correspond, it is called comparing.

3. Invention is an operation of the sensorium, by which we voluntarily continue to excite one train of ideas, suppose the design of raising water by a machine; and at the same time attend to all other ideas, which are connected with this by every kind of catenation; and combine or separate them voluntarily for the purpose of obtaining some end.

For we can create nothing new, we can only combine or separate the ideas, which we have already received by our perceptions: thus if I wish to represent a monster, I call to my mind the ideas of every thing disagreeable and horrible, and combine the nastiness and gluttony of a hog, the stupidity and obstinacy of an ass, with the fur and awkwardness of a bear, and call the new combination Caliban. Yet such a monster may exist in nature, as all his attributes are parts of nature. So when I wish to represent every thing, that is excellent, and amiable; when I combine benevolence with cheerfulness, wisdom, knowledge, taste, wit, beauty of person, and elegance of manners, and associate them in one lady as a pattern to the world, it is called invention; yet such a person may exist,—such a person does exist!—It is —— ——, who is as much a monster as Caliban.

4. In respect to consciousness, we are only conscious of our existence, when we think about it; as we only perceive the lapse of time, when we attend to it; when we are busied about other objects, neither the lapse of time nor the consciousness of our own existence can occupy our attention. Hence, when we think of our own existence, we only excite abstracted or reflex ideas (as they are termed), of our principal pleasures or pains, of our desires or aversions, or of the figure, solidity, colour, or other properties of our bodies, and call that act of the sensorium a consciousness of our existence. Some philosopher, I believe it is Des Cartes, has said, "I think, therefore I exist." But this is not right reasoning, because thinking is a mode of existence; and it is thence only saying, "I exist, therefore I exist." For there are three modes of existence, or in the language of grammarians three kinds of verbs. First, simply I am, or exist. Secondly, I am acting, or exist in a state of activity, as I move. Thirdly, I am suffering, or exist in a state of being acted upon, as I am moved. The when, and the where, as applicable to this existence, depends on the successive motions of our own or of other bodies; and on their respective situations, as spoken of Sect. XIV. 2. 5.

5. Our identity is known by our acquired habits or catenated trains of ideas and muscular motions; and perhaps, when we compare infancy with old age, in those alone can our identity be supposed to exist. For what else is there of similitude between the first speck of living entity and the mature man?—every deduction of reasoning, every sentiment or passion, with every fibre of the corporeal part of our system, has been subject almost to annual mutation; while some catenations alone of our ideas and muscular actions have continued in part unchanged.

By the facility, with which we can in our waking hours voluntarily produce certain successive trains of ideas, we know by experience, that we have before reproduced them; that is, we are conscious of a time of our existence previous to the present time; that is, of our identity now and heretofore. It is these habits of action, these catenations of ideas and muscular motions, which begin with life, and only terminate with it; and which we can in some measure deliver to our posterity; as explained in Sect. XXXIX.

6. When the progressive motions of external bodies make a part of our present catenation of ideas, we attend to the lapse of time; which appears the longer, the more frequently we thus attend to it; as when we expect something at a certain hour, which much interests us, whether it be an agreeable or disagreeable event; or when we count the passing seconds on a stop-watch.

When an idea of our own person, or a reflex idea of our pleasures and pains, desires and aversions, makes a part of this catenation, it is termed consciousness; and if this idea of consciousness makes a part of a catenation, which we excite by recollection, and know by the facility with which we excite it, that we have before experienced it, it is called identity, as explained above.

7. In respect to freewill, it is certain, that we cannot will to think of a new train of ideas, without previously thinking of the first link of it; as I cannot will to think of a black swan, without previously thinking of a black swan. But if I now think of a tail, I can voluntarily recollect all animals, which have tails; my will is so far free, that I can pursue the ideas linked to this idea of tail, as far as my knowledge of the subject extends; but to will without motive is to will without desire or aversion; which is as absurd as to feel without pleasure or pain; they are both solecisms in the terms. So far are we governed by the catenations of motions, which affect both the body and the mind of man, and which begin with our irritability, and end with it.

* * * * *

SECT. XVI.

OF INSTINCT.

Haud equidem credo, quia sit divinitus illis Ingenium, aut rerum fato prudentia major.—Virg. Georg. L. I. 415.

I. Instinctive actions defined. Of connate passions. II. Of the sensations and motions of the foetus in the womb. III. Some animals are more perfectly formed than others before nativity. Of learning to walk. IV. Of the swallowing, breathing, sucking, pecking, and lapping of young animals. V. Of the sense of smell, and its uses to animals. Why cats do not eat their kittens. VI. Of the accuracy of sight in mankind, and their sense of beauty. Of the sense of touch in elephants, monkies, beavers, men. VII. Of natural language. VIII. The origin of natural language; 1. the language of fear; 2. of grief; 3. of tender pleasure; 4. of serene pleasure; 5. of anger; 6. of attention. IX. Artificial language of turkies, hens, ducklings, wagtails, cuckoos, rabbits, dogs, and nightingales. X. Of music; of tooth-edge; of a good ear; of architecture. XI. Of acquired knowledge; of foxes, rooks, fieldfares, lapwings, dogs, cats, horses, crows, and pelicans. XII. Of birds of passage, dormice, snakes, bats, swallows, quails, ringdoves, stare, chaffinch, hoopoe, chatterer, hawfinch, crossbill, rails and cranes. XIII. Of birds nests; of the cuckoo; of swallows nests; of the taylor bird. XIV. Of the old soldier; of haddocks, cods, and dog fish; of the remora; of crabs, herrings, and salmon. XV. Of spiders, caterpillars, ants, and the ichneumon. XVI. 1. Of locusts, gnats; 2. bees; 3. dormice, flies, worms, ants, and wasps. XVII. Of the faculty that distinguishes man from the brutes.

I. All those internal motions of animal bodies, which contribute to digest their aliment, produce their secretions, repair their injuries, or increase their growth, are performed without our attention or consciousness. They exist as well in our sleep, as in our waking hours, as well in the foetus during the time of gestation, as in the infant after nativity, and proceed with equal regularity in the vegetable as in the animal system. These motions have been shewn in a former part of this work to depend on the irritations of peculiar fluids, and as they have never been classed amongst the instinctive actions of animals, are precluded from our present disquisition.

But all those actions of men or animals, that are attended with consciousness, and seem neither to have been directed by their appetites, taught by their experience, nor deduced from observation or tradition, have been referred to the power of instinct. And this power has been explained to be a divine something, a kind of inspiration; whilst the poor animal, that possesses it, has been thought little better than a machine!

The irksomeness, that attends a continued attitude of the body, or the pains, that we receive from heat, cold, hunger, or other injurious circumstances, excite us to general locomotion: and our senses are so formed and constituted by the hand of nature, that certain objects present us with pleasure, others with pain, and we are induced to approach and embrace these, to avoid and abhor those, as such sensations direct us.

Thus the palates of some animals are gratefully affected by the mastication of fruits, others of grains, and others of flesh; and they are thence instigated to attain, and to consume those materials; and are furnished with powers of muscular motion, and of digestion proper for such purposes.

These sensations and desires constitute a part of our system, as our muscles and bones constitute another part: and hence they may alike be termed natural or connate; but neither of them can properly be termed instinctive: as the word instinct in its usual acceptation refers only to the actions of animals, as above explained: the origin of these actions is the subject of our present enquiry.

The reader is intreated carefully to attend to this definition of instinctive actions, lest by using the word instinct without adjoining any accurate idea to it, he may not only include the natural desires of love and hunger, and the natural sensations of pain or pleasure, but the figure and contexture of the body, and the faculty of reason itself under this general term.

II. We experience some sensations, and perform some actions before our nativity; the sensations of cold and warmth, agitation and rest, fulness and inanition, are instances of the former; and the repeated struggles of the limbs of the foetus, which begin about the middle of gestation, and those motions by which it frequently wraps the umbilical chord around its neck or body, and even sometimes ties it on a knot; are instances of the latter. Smellie's Midwifery, (Vol. I. p. 182.)

By a due attention to these circumstances many of the actions of young animals, which at first sight seemed only referable to an inexplicable instinct, will appear to have been acquired like all other animal actions, that are attended with consciousness, by the repeated efforts of our muscles under the conduct of our sensations or desires.

The chick in the shell begins to move its feet and legs on the sixth day of incubation (Mattreican, p. 138); or on the seventh day, (Langley); afterwards they are seen to move themselves gently in the liquid that surrounds them, and to open and shut their mouths, (Harvei, de Generat. p. 62, and 197. Form de Poulet. ii. p. 129). Puppies before the membranes are broken, that involve them, are seen to move themselves, to put out their tongues, and to open and shut their mouths, (Harvey, Gipson, Riolan, Haller). And calves lick themselves and swallow many of their hairs before their nativity: which however puppies do not, (Swammerden, p. 319. Flemyng Phil. Trans. Ann. 1755. 42). And towards the end of gestation, the foetus of all animals are proved to drink part of the liquid in which they swim, (Haller. Physiol. T. 8. 204). The white of egg is found in the mouth and gizzard of the chick, and is nearly or quite consumed before it is hatched, (Harvie de Generat. 58). And the liquor amnii is found in the mouth and stomach of the human foetus, and of calves; and how else should that excrement be produced in the intestines of all animals, which is voided in great quantity soon after their birth; (Gipson, Med. Essays, Edinb. V. i. 13. Halleri Physiolog. T. 3. p. 318. and T. 8). In the stomach of a calf the quantity of this liquid amounted to about three pints, and the hairs amongst it were of the same colour with those on its skin, (Blasii Anat. Animal, p.m. 122). These facts are attested by many other writers of credit, besides those above mentioned.

III. It has been deemed a surprising instance of instinct, that calves and chickens should be able to walk by a few efforts almost immediately after their nativity: whilst the human infant in those countries where he is not incumbered with clothes, as in India, is five or six months, and in our climate almost a twelvemonth, before he can safely stand upon his feet.

The struggles of all animals in the womb must resemble their mode of swimming, as by this kind of motion they can best change their attitude in water. But the swimming of the calf and chicken resembles their manner of walking, which they have thus in part acquired before their nativity, and hence accomplish it afterwards with very few efforts, whilst the swimming of the human creature resembles that of the frog, and totally differs from his mode of walking.

There is another circumstance to be attended to in this affair, that not only the growth of those peculiar parts of animals, which are first wanted to secure their subsistence, are in general furthest advanced before their nativity: but some animals come into the world more completely formed throughout their whole system than others: and are thence much forwarder in all their habits of motion. Thus the colt, and the lamb, are much more perfect animals than the blind puppy, and the naked rabbit; and the chick of the pheasant, and the partridge, has more perfect plumage, and more perfect eyes, as well as greater aptitude to locomotion, than the callow nestlings of the dove, and of the wren. The parents of the former only find it necessary to shew them their food, and to teach them to take it up; whilst those of the latter are obliged for many days to obtrude it into their gaping mouths.

IV. From the facts mentioned in No. 2. of this Section, it is evinced that the foetus learns to swallow before its nativity; for it is seen to open its mouth, and its stomach is found filled with the liquid that surrounds it. It opens its mouth, either instigated by hunger, or by the irksomeness of a continued attitude of the muscles of its face; the liquor amnii, in which it swims, is agreeable to its palate, as it consists of a nourishing material, (Haller Phys. T. 8. p. 204). It is tempted to experience its taste further in the mouth, and by a few efforts learns to swallow, in the same manner as we learn all other animal actions, which are attended with consciousness, by the repeated efforts of our muscles under the conduct of our sensations or volitions.

The inspiration of air into the lungs is so totally different from that of swallowing a fluid in which we are immersed, that it cannot be acquired before our nativity. But at this time, when the circulation of the blood is no longer continued through the placenta, that suffocating sensation, which we feel about the precordia, when we are in want of fresh air, disagreeably affects the infant: and all the muscles of the body are excited into action to relieve this oppression; those of the breast, ribs, and diaphragm are found to answer this purpose, and thus respiration is discovered, and is continued throughout our lives, as often as the oppression begins to recur. Many infants, both of the human creature, and of quadrupeds, struggle for a minute after they are born before they begin to breathe, (Haller Phys. T. 8. p. 400. ib pt. 2. p. 1). Mr. Buffon thinks the action of the dry air upon the nerves of smell of new-born animals, by producing an endeavour to sneeze, may contribute to induce this first inspiration, and that the rarefaction of the air by the warmth of the lungs contributes to induce expiration, (Hist. Nat. Tom. 4. p. 174). Which latter it may effect by producing a disagreeable sensation by its delay, and a consequent effort to relieve it. Many children sneeze before they respire, but not all, as far as I have observed, or can learn from others.

At length, by the direction of its sense of smell, or by the officious care of its mother, the young animal approaches the odoriferous rill of its future nourishment, already experienced to swallow. But in the act of swallowing, it is necessary nearly to close the mouth, whether the creature be immersed in the fluid it is about to drink, or not: hence, when the child first attempts to suck, it does not slightly compress the nipple between its lips, and suck as an adult person would do, by absorbing the milk; but it takes the whole nipple into its mouth for this purpose, compresses it between its gums, and thus repeatedly chewing (as it were) the nipple, presses out the milk, exactly in the same manner as it is drawn from the teats of cows by the hands of the milkmaid. The celebrated Harvey observes, that the foetus in the womb must have sucked in a part of its nourishment, because it knows how to suck the minute it is born, as any one may experience by putting a finger between its lips, and because in a few days it forgets this art of sucking, and cannot without some difficulty again acquire it, (Exercit. de Gener. Anim. 48). The same observation is made by Hippocrates.

A little further experience teaches the young animal to suck by absorption, as well as by compression; that is, to open the chest as in the beginning of respiration, and thus to rarefy the air in the mouth, that the pressure of the denser external atmosphere may contribute to force out the milk.

The chick yet in the shell has learnt to drink by swallowing a part of the white of the egg for its food; but not having experienced how to take up and swallow solid seeds, or grains, is either taught by the felicitous industry of its mother; or by many repeated attempts is enabled at length to distinguish and to swallow this kind of nutriment.

And puppies, though they know how to suck like other animals from their previous experience in swallowing, and in respiration; yet are they long in acquiring the art of lapping with their tongues, which from the flaccidity of their cheeks, and length of their mouths, is afterwards a more convenient way for them to take in water.

V. The senses of smell and taste in many other animals greatly excel those of mankind, for in civilized society, as our victuals are generally prepared by others, and are adulterated with salt, spice, oil, and empyreuma, we do not hesitate about eating whatever is set before us, and neglect to cultivate these senses: whereas other animals try every morsel by the smell, before they take it into their mouths, and by the taste before they swallow it: and are led not only each to his proper nourishment by this organ of sense, but it also at a maturer age directs them in the gratification of their appetite of love. Which may be further understood by considering the sympathies of these parts described in Class IV. 2. 1. 7. While the human animal is directed to the object of his love by his sense of beauty, as mentioned in No. VI. of this Section. Thus Virgil. Georg. III. 250.

Nonne vides, ut tota tremor pertentat equorum Corpora, si tantum notas odor attulit auras? Nonne canis nidum veneris nasutus odore Quaerit, et erranti trahitur sublambere lingua? Respuit at gustum cupidus, labiisque retractis Elevat os, trepidansque novis impellitur aestris Inserit et vivum felici vomere semen.— Quam tenui filo caecos adnectit amores Docta Venus, vitaeque monet renovare favillam!—ANON.

The following curious experiment is related by Galen. "On dissecting a goat great with young I found a brisk embryon, and having detached it from the matrix, and snatching it away before it saw its dam, I brought it into a certain room, where there were many vessels, some filled with wine, others with oil, some with honey, others with milk, or some other liquor; and in others were grains and fruits; we first observed the young animal get upon its feet, and walk; then it shook itself, and afterwards scratched its side with one of its feet: then we saw it smelling to every one of these things, that were set in the room; and when it had smelt to them all, it drank up the milk." L. 6. de locis. cap. 6.

Parturient quadrupeds, as cats, and bitches, and sows, are led by their sense of smell to eat the placenta as other common food; why then do they not devour their whole progeny, as is represented in an antient emblem of TIME? This is said sometimes to happen in the unnatural state in which we confine sows; and indeed nature would seem to have endangered her offspring in this nice circumstance! But at this time the stimulus of the milk in the tumid teats of the mother excites her to look out for, and to desire some unknown circumstance to relieve her. At the same time the smell of the milk attracts the exertions of the young animals towards its source, and thus the delighted mother discovers a new appetite, as mentioned in Sect. XIV. 8. and her little progeny are led to receive and to communicate pleasure by this most beautiful contrivance.

VI. But though the human species in some of their sensations are much inferior to other animals, yet the accuracy of the sense of touch, which they possess in so eminent a degree, gives them a great superiority of understanding; as is well observed by the ingenious Mr. Buffon. The extremities of other animals terminate in horns, and hoofs, and claws, very unfit for the sensation of touch; whilst the human hand is finely adapted to encompass its object with this organ of sense.

The elephant is indeed endued with a fine sense of feeling at the extremity of his proboscis, and hence has acquired much more accurate ideas of touch and of sight than most other creatures. The two following instances of the sagacity of these animals may entertain the reader, as they were told me by some gentlemen of distinct observation, and undoubted veracity, who had been much conversant with our eastern settlements. First, the elephants that are used to carry the baggage of our armies, are put each under the care of one of the natives of Indostan, and whilst himself and his wife go into the woods to collect leaves and branches of trees for his food, they fix him to the ground by a length of chain, and frequently leave a child yet unable to walk, under his protection: and the intelligent animal not only defends it, but as it creeps about, when it arrives near the extremity of his chain, he wraps his trunk gently round its body, and brings it again into the centre of his circle. Secondly, the traitor elephants are taught to walk on a narrow path between two pit-falls, which are covered with turf, and then to go into the woods, and to seduce the wild elephants to come that way, who fall into these wells, whilst he passes safe between them: and it is universally observed, that those wild elephants that escape the snare, pursue the traitor with the utmost vehemence, and if they can overtake him, which sometimes happens, they always beat him to death.

The monkey has a hand well enough adapted for the sense of touch, which contributes to his great facility of imitation; but in taking objects with his hands, as a stick or an apple, he puts his thumb on the same side of them with his fingers, instead of counteracting the pressure of his fingers with it: from this neglect he is much slower in acquiring the figures of objects, as he is less able to determine the distances or diameters of their parts, or to distinguish their vis inertiae from their hardness. Helvetius adds, that the shortness of his life, his being fugitive before mankind, and his not inhabiting all climates, combine to prevent his improvement. (De l'Esprit. T. 1. p.) There is however at this time an old monkey shewn in Exeter Change, London, who having lost his teeth, when nuts are given him, takes a stone into his hand, and cracks them with it one by one; thus using tools to effect his purpose like mankind.

The beaver is another animal that makes much use of his hands, and if we may credit the reports of travellers, is possessed of amazing ingenuity. This however, M. Buffon affirms, is only where they exist in large numbers, and in countries thinly peopled with men; while in France in their solitary state they shew no uncommon ingenuity.

Indeed all the quadrupeds, that have collar-bones, (claviculae) use their fore-limbs in some measure as we use our hands, as the cat, squirrel, tyger, bear and lion; and as they exercise the sense of touch more universally than other animals, so are they more sagacious in watching and surprising their prey. All those birds, that use their claws for hands, as the hawk, parrot, and cuckoo, appear to be more docile and intelligent; though the gregarious tribes of birds have more acquired knowledge.

Now as the images, that are painted on the retina of the eye, are no other than signs, which recall to our imaginations the objects we had before examined by the organ of touch, as is fully demonstrated by Dr. Berkley in his treatise on vision; it follows that the human creature has greatly more accurate and distinct sense of vision than that of any other animal. Whence as he advances to maturity he gradually acquires a sense of female beauty, which at this time directs him to the object of his new passion.

Sentimental love, as distinguished from the animal passion of that name, with which it is frequently accompanied, consists in the desire or sensation of beholding, embracing, and saluting a beautiful object.

The characteristic of beauty therefore is that it is the object of love; and though many other objects are in common language called beautiful, yet they are only called so metaphorically, and ought to be termed agreeable. A Grecian temple may give us the pleasurable idea of sublimity, a Gothic temple may give us the pleasurable idea of variety, and a modern house the pleasurable idea of utility; music and poetry may inspire our love by association of ideas; but none of these, except metaphorically, can be termed beautiful; as we have no wish to embrace or salute them.