Motion.

Of Animal zontally, as on walking on level ground, but to bear it up against its own weight, by means of the extensors of the knee of the advanced leg, and those of the heel of that which is behind; this is the reason of the knee and calf of the leg being fatigued in ascending; and the fatigue is relieved by inclining the body forward, because then the lever by which its weight acts on the knee is shortened.

Running is only a succession of short leaps, and it will be understood from what we shall presently say of leaping.

137 Walking When a quadruped waiks, he first slightly bends the on four feet. articulations of the hind legs, and then extends them, in order to carry forward the body, which motion is considerably aided by the extensors of the knee and the heel. The breast being thus thrown forward, the fore legs incline backward, and the animal would fall, did it not instantly throw them forward in order to support itself. It then draws up the trunk upon the fore legs, and renews its former efforts.

138 Leaping.

In this walking, each step is performed by two legs, one belonging to the fore, and the other to the hind pair. Sometimes these are of the same side, and sometimes those of opposite sides. The motion of a horse who steps forward in the latter way, is termed a pace.

In the animals that have the fore feet longer than the hind, and have their strength chiefly in the anterior part of the body, the principal impulse is given by extending the fore foot. The hind foot then rises to follow it, and it is not until the moment that the latter extends itself in its turn, that the fore foot is raised. This is the manner in which the giraffe is said to move. But when the fore legs are considerably disproportioned to the others, and particularly when the posterior extremities are feebly and badly articulated, as in the sloths, the animal is obliged to drag itself forward, by first extending the fore legs, and then ending them so as to draw the body after them. Hence the progression of the sloth is so laborious.

Those animals which have their fore legs very short in proportion to their hind legs, would be incapable of sufficiently supporting their bodies, and must fall for ward on each impulse of the latter, had they not the precaution to make a prancing movement; that is, to raise the anterior extremities entirely off the ground, previously to their being impelled onward by means of the bind feet. Accordingly, such animals cannot in propriety of language be said to walk; they only move forward by leaps. This is the case with hares, rats, and particularly jerboas. Indeed, these animals cannot be said to walk at all, except in the action of ascending. When they attempt to walk slowly on level ground, they are obliged to move themselves by the fore feet, and merely to drag after them the hind pair. This may be observed in rabbits, and still more distinctly in frogs.

In leaping, the body rises completely from the earth, and remains without any support for a short period, the duration of which depends on the force with which the leap has been made. This action is performed by a sudden extension of all the muscles belonging to the sacral articulations, immediately after they have undergone an unusual degree of flection. By this general extension these articulations receive a violent motion, the impulse of which is communicated to the centre of gravity of

the body, and it is thus projected with a determined ve- Of Animal locity, which is more or less in opposition to its weight. Motion. The projectile force and extent of the leap depend on the proportional length of the bones, and strength of the muscles. Those animals, therefore, leap best that have the sacral extremities longer and thicker than the atlantal; as the kangaroos, jerboas, frogs, alticæ, grylli, fleas, &c.

Small animals leap proportionally much farther than the larger species; and we know of none whose muscular strength, in this way, can be put in competition with that of a flea, which in a moderate computation is known to leap to a distance of at least 200 times its own length. The direction of a leap depends on the situation of the centre of gravity with respect to the member by which the impulse is given. Hence, only man and birds can leap vertically, because they alone have the trunk situated above the members by which the leap is effected. Quadrupeds, and most insects, can only leap forward; but spiders, which have several long feet on each side of their body, can also leap sideways.

139

Running consists of a series of low leaps performed Running. alternately by each leg. It differs from walking, in the body being projected forward at each step, and in the hind foot being raised before the anterior touches the ground. It is more rapid than the quickest walk, because the acquired velocity is preserved, and increased at each bound by a new velocity. Running, therefore, cannot be instantaneously suspended, though a stop may be put to walking at each step.

In running, the animal inclines its body forward, that the centre of gravity may be in a proper position for receiving an impulse in that direction from the hind leg; and it is obliged to move the fore leg rapidly forward, to guard against falling.

Man varies his manner of running, only by taking longer or shorter steps, or giving to this motion a greater or less degree of rapidity; but quadrupeds vary this motion by the different order in which they raise each foot, or bring it to the ground.

140

Trotting is a mode of running in which the feet dia- Trotting gonally opposite rise at once, and fall at once, each pair alternately, but in such a manner, that for a moment all the four feet are off the ground. This produces a regular motion, and the sound of the animal's steps are heard two and two in succession.

141

Galloping is a running motion in which the animal Galoping. raises the anterior feet at each step, and throws the body forward by the extension of the posterior feet. When the two fore-feet descend at the same time, and are followed by the two hind feet also descending together, the motion is called a full gallop, which is the most rapid a horse can perform, and the only mode of running in dogs, hares, &c. In this kind of gallop the stops of the horse are likewise heard by two beats at a time. The common gallop is when the two fore-feet are lifted unequally, and fall one after another. This may be divided into gallops in which the horses footsteps are heard by a series of three or four beats, because the posterior feet may fall to the ground either both together, or one after the other.

There are several kinds of animals which leap by the means of organs different from feet, but always by a sudden extension of several articulations. Serpents leap by folding their bodies into several un3 P2 dulations,

Of Animal dulations, which they unbend all at once, according as Motion. they wish to give more or less velocity to their motion; some may be assisted by the scales of their belly, which they can elevate and depress, but only a few genera are capable of employing this means.

142 Climbing.

143

Flying.

Some fishes also leap to the tops of cataracts by bending their bodies strongly, and afterwards unbending them with an elastic spring.

The long-tailed crayfishes, particularly the shrimps, leap by extending the tail after it has been previously bent under the body.

The larva of the fly, vulgarly called the maggot, forms itself into a circle, contracts itself as much as possible, then suddenly unbending, darts forwards to a considerable distance.

The motion of climbing, so useful to many of the inferior animals, consists, in hanging from, and strongly grasping any object susceptible of being seized by the fingers, toes, or tail, and thus rising, by successive efforts, in a direction opposite to the animal's weight. From this explanation, it is evident that those animals which have the divisions of their extremities most distinct and flexible, will be the best climbers; and accordingly we find that the animals called quadrumanous, as the apes, lemurs, and a few others, perform this action in the most perfect manner. Man is but an indifferent climber, as he can only grasp with his hands. In oppossums, ant-eaters and sloths, one of the toes is distinct, like the thumb in man, apes, and lemurs; or else they have a considerable protuberance on the heel, which has the same effect. Many animals, as some of the monkeys, some species of oppossum and ant-eater, the manis, &c. have a very flexible prehensile tail, which assists them in climbing. The animals of the cat genus have very sharp talons, by which they are materially assisted in this kind of progression, as they enable them to adhere firmly to the bark of trees, &c. Creepers, nut-hatches, woodpeckers, and other climbing birds, support themselves in a similar manner.

The motion of flying, by which an animal can sup. port itself for some considerable time in the air, can properly be said to be performed only by birds: for though bats can imitate this motion with tolerable success, and the galiopithecus, flying squirrels, and flying oppossums, appear to fly from one tree to another, the motion of the former cannot be supported for so long a time as that of birds; and the motion of the latter animals can be considered only as a leap, assisted and prolonged by the opposition given to the air, by the membranous expansion between their limbs.

When a bird designs to fly, it first darts into the air, either by leaping from the ground, or by throwing itself from some height. In the mean time it raises the whole of the wings which had till then remained folded, and which it unfolds in a horizontal direction by extending the bones. When the wings have thus acquired all the superficial extent of which they are susceptible, they are suddenly depressed, till they form, with the vertical plane of the body, an angle that is obtuse upward, and acute downward. The resistance which the air gives to this motion suddenly performed in it, produces a reaction on the body of the bird, and thus moves it forward as in ordinary leaps. This impulse once given, the bird refolds the wings by bending the joints, and

repeats its efforts by another stroke. As the velocity Of Animal thus acquired in ascending is gradually diminished by Motion. the effect of gravitation, a moment occurs in which it ceases, and in which the bird tends neither to ascend nor descend. If at this moment it gives a new stroke with the wings, it acquires a new ascending velocity, by which it will be carried as far as before, and by repeating these efforts, it will ascend in a uniform manner. If this second stroke be made before the velocity first acquired is lost, an additional impulse will be received; and by a continuance of this action the bird will ascend with an accelerated motion. If the wings do not vibrate when the ascending velocity is lost, the bird will begin to descend; and if it allow itself to fall down to the point from which it set out, it cannot ascend as high as at first, but by a much stronger exertion of the wings; but if it seizes in the fall a point so situated that the acquired descending velocity, and the small space which it has to fall down reciprocally balance each other, it may, by a series of equal vibrations, keep itself at the same height.

When a bird wishes to descend rapidly, as when it darts upon its prey, it altogether suppresses the vibration of its wings, and thus falls by its own gravity, While descending, however, it may suddenly break its fall by extending its wings, and this suspension is called a recover.

We have as yet considered only the vertical flight of“ a bird. To fly horizontally, it must rise in an oblique direction, and make a new movement of its wings, when it is ready to descend below the point from which it departed; but in this way it will not fly in a straight line, but will describe a series of curves so very much depressed, that the horizontal will overcome the vertical motion. In order to ascend obliquely, the bird must make quicker vibrations of its wings, and to ascend in a similar direction, the vibrations must be slower.

The deviations of flight to the right or left are chiefly produced by the unequal vibrations of the opposite wing; those of the left wing carrying the bird to the right, and vice versa. The more rapid the flight is forward, the greater is the difficulty of one wing surpassing the other in the velocity of its vibrations, and of course the deviation sideways is the more difficult. Hence birds which fly with the greatest velocity make large circles in turning.

The tail, when spread out, contributes to sustain the posterior part of the body. If it is depressed when the bird has acquired a progressive velocity, it presents an obstacle which elevates the posterior part of the body, and depresses the anterior. If it is turned up, the contrary effect is produced. Some birds incline to one side, to assist them like a rudder, when they wish to change their horizontal direction,

The structure of most birds peculiarly adapts them for rapid motion through the air, and for sustaining themselves in this element with the greatest facility. See ORNITHOLOGY, No 37.

144

The action of swimming, like that of flying, nearly sin ming resembles leaping, except that, like flying, the leap does not take place on a fixed surface. A great variety of animals, besides fish, and most of the other inhabitants of the waters, are capable of swimming. This action is performed with considerable ease by several of the mam

Of Animal malia, even by the bulky elephant, and the unwieldy Motion hippopotamus; by many tribes of birds; by several reptiles and serpents, and by some insects.

145.

146

147

motions.

The organs employed by fishes, in making their way through the water, are their fins, tail, and air-bladder; the two former exerting the necessary motions like the wings of birds, while the latter, by being compressed or expanded, causes the necessary changes in the specific gravity of the body, and thereby renders the animal more or less buoyant. The swimming of fishes has been treated of with sufficient minuteness under ICHTHYOLOGY, chap. iii. sect. 3. to which we refer the reader. The cetacea employ much the same means as fishes; but in them the principal efforts of the tail are made in a vertical direction, and the use of the air-bag is supplied by lungs, which they can compress and dilate at pleasure, by the action of the diaphragm, or the intercostal muscles. See CETOLOGY.

The swimming of mammalia, and of water birds, is performed by means of the legs and feet, which are used like oars, to propel the body forward by the resistance which they make to the water in the contrary direction. Hence those quadrupeds and birds that have flat or webbed feet, swim most easily, as the resisting surface is the greatest. Of all the mammalia, man has the most occasion to use his hands in swimming, on account of the greater proportional weight of his head.

Serpents, and the larva of such insects as sometimes inhabit the waters, perform the action of swimming by rapid inflections of the body like an eel or a leech. The larvae that are most commonly found in the waters are those of the water beetles, the hydrophilus, the day flies, the aquatic tipule, and gnats.

No animal walks without legs, or flies without wings (if we except the flying fish, whose fins enable it rather to spring than fly); but there are many that swim without fins, and that leap or creep without any legs. The rapidity of movement is not proportioned to the number of instruments that are employed: if the spout-fish be observed to move slowly with one leg, the sea-urchin moves still more slowly with many thousands; the oyster moves by squirting out water; the scallop by the jerk of its shell, and when in the water it rises to the surface and sails before the wind.

Many animals are formed by nature to fly, walk, leap, and swim the fate of those are rather uncommon whose muscles or feet are by nature attached to their integuments; the lobster is obliged to throw off its shell, and the caterpillar all its feet, with the skins, and in that situation to remain stationary till it receive new instruments of motion.

Whoever has read the celebrated work De Motu Animalium, needs not to be told that, besides the organs which are here mentioned, the form, the structure, and even the specific gravity of the body, as depending on the nature of the bones and muscles, or as varied by air-vesicles and bubbles, with a great variety of other circumstances, are necessary to explain the different phenomena of locomotion.

Vegetable As to vegetable motions, they evidently depend on external agents: the wings of seeds only fit them to be carried by the wind, their specific gravity to float in the water, and their legs or tentacula to adhere to bodies that are in motion; the singular motions which have

been ascribed to sleeping, to waking, to sensation, and Of Animal volition, in the vegetable kingdom, seem only the con- Motion. sequence of light, heat, moisture, and such stimulants, acting invisibly or with secret influence: the opening and closing of the meteoric flowers are always corre spondent to the states of the atmosphere; and the opening and closing of the equinoctial and tropic flowers, to the light, the length or shortness of the day. The principal intentions of locomotion are to get Uses of lofood, to shun danger, to promote intercourse and di-comotion, sperse the species.

There is perhaps no part of physiology which is more important than the relations which subsist between the different functions of the living body; but it is a part of the subject which is as yet but little understood. We regret that our limits will not permit us to pay all the attention to it which we could wish. We shall, however, briefly notice under each function, the principal relations that are found to take place between it and those which have been previously considered.

148

149

Besides the dependence which animal motion has, in Mutual remost instances, on the nervous system, (see N° 111.) we lations befind an evident sympathy between these two functions tween senin a variety of phenomena. A violent emotion or im-sation and pression on the nerves often throws the limbs into con- motion. vulsive agitations; spasmodic affections are relieved, or sometimes removed, by the coming on of deliriunt; and these symptions will alternate with each other: a compression of the brain, or of some large nervous trunk, produces general or partial want of motion, and when this compression is removed, the muscles for the most part recover their usual action; an attack of epilepsy is often preceded by the sensation of a stream of vapour commencing in some external part, and rising to the brain. These, and many other phenomena that might be mentioned, fully prove the sympathy between the nervous and muscular systems; and with this enumeration we must dismiss the subject.

CHAP. V. Of Digestion.

THE necessity of repairing the waste of the body is Appetite announced in all animals by the feelings of hunger and for food. thirst; the former of which intimates the occasion for solid, the latter for liquid food. This imperious necessity overrules all the other affections of the vital principle, and every other appetite often remains suspended till that necessity be satisfied. It is difficult to assign the final cause of these singular sensations, but probably our researches on that subject are rather curious than useful. Whatever be the ultimate end of these appetites, we readily perceive how much they are influenced by habit. We find that when we are accustomed to take food at particular times, the appetite, under ordinary circumstances, always reminds us at these times, of the occasion, whether real or apparent, for receiving a new supply. By this influence of habit some animals, especially man, are accustomed to take several meals in a day, while others can fast for days, or even weeks, together. The appetite for food also varies considerably at different ages. It is more lively and more imperious in infancy and early childhood, and in general in those animals who have not yet acquired their full growth; it is on the contrary weaker in advanced age, and when the body ceases to increaso

Of

increase in size. It is more frequently renewed in the Digestion. strong and healthy, and those who are accustomed to laborious occupations or active exercises.

151

152 Plants and some ani mals live on water and

We know that in the natural state of the animal body, the appetite for food is influenced by the nature of the aliment on which the animal is accustomed to subsist. Many animals live entirely on vegetable food, and these have no appetite for animal substances, and even reject these when offered to them. On the other hand, many tribes live entirely on animal food, and either refuse vegetable, or, if obliged by necessity to employ it as food, do not appear to derive nourishment from it. We find, however, that it is in the power of habit to remove these appetites; that a horse or a sheep may be taught to live on animal food, while a dog or a cat may be supported entirely on vegetable substances. A few animals are capable of subsisting on almost every kind of animal or vegetable substances, or are omnivorous.

Many animals are capable of being supported by water and air alone. We know that several fishes, as the minow, the gold and silver fish, &c. will live for a long air alone. time in a vessel containing pure water, and freely exposed to the air. Rondelet a celebrated writer on fishes in the 16th century) relates a remarkable instance of this. He kept a fish during three years in a vessel that was constantly full of very pure water. It grew to such a size, that at the end of that time the vessel could no longer contain it. Leeches are often kept for several years with no other nutriment but water, and that not very often changed. There is good reason to believe that the sole food of plants consists of water and air, and that the soil in which they grow answers scarcely any other purpose than that of preserving and conducting those necessary aliments.

253

154 Differences of digestion

.

It has been supposed that some animals are capable of, subsisting on matters that appear to contain no nutritious principles, such as sand, hair, and wool. Borelli long ago conceived this opinion, from observing that in many te-staceous animals which he dissected, the alimentary tube contained nothing but sand. It has often been remarked, that horses, cows, and sheep, when deprived of their usual nourishment, will lick their bodies, and swallow down the hair, or, in the case of sheep, will tear off and swallow each others wool. If we consider the nature of these substances, we think there is no reason to suppose that they answer any other purpose than distending the alimentary canal or stomach, and thus in some measure counteracting the effect of hunger.

The subject of food in general has been already treated of, under ALIMENT, and in MATERIA MEDICA, Part I. No 17; and the function of digestion, as far as it relates to man, has been considered under ANATOMY, No 106, 107, and under CHEMISTRY, N° 2548. It remains for us here only to make a few observations on the comparative physiology of this fur ction.

Digestion differs considerably in the various classes of animals, both as to the organs by which it is performed, and as to the simplicity or complex nature of the operation itself. The general variations that take place in the organs of digestion, have been mentioned under the comparative part of ANATOMY, N° 152, and are fully treated of by Cuvier, in his Leçons d'Anatomie Comparé, tom. iii. and Blumenbach, in his Comparative Anatomy, chap. 6. and 7.

In the more perfect animals, digestion supposes a 5

Of

series of operations, from the time that the food enters the mouth, till the nutritious parts of it are taken into Digestion. the circulating system. These operations are, mustication, insalivation, deglutition, chymification, and chylification.

155

Mastication is performed by means of teeth, and there- Masticafore can scarcely be said to take place in those animals tion. that are not furnished with these organs. We know that all mammalia, except those which Cuvier calls edentata, as the ant-eaters, pangolins, and platypus, have teeth, fitted both for dividing and chewing their food; but here an important difference takes place. Those animals which live chiefly on animal food, ..ve most of their teeth sharp and pointed, for the purpose of seizing and tearing their prey, while the graminivorous and granivorous animals have very large and strong grinders, in which the hard substance commonly called enamel (or what Blake calls corpus striatum,*) forms alternate * Blake on layers with the bony part. Such are also found in most reptiles and serpents, and in many fishes; but in some of these they seem less to serve the purpose of dividing the of food, than to seize and retain it till swallowed. Birds Teeth. have no teeth, though some of them have the mandibles of the bill so formed as to divide and cut in pieces their food.

the Struc

ture and Formation the

tion.

136

During mastication the food is mixed with the saliva, Insalivaand is thus better fitted for easy solution in the stomach. This insalivation of the food mav, however, take place, without previous mastication. It is common for ser pents to swallow their food whole; but in order to facilitate its pas-age down the throat, they first besmear it all over with their muscous saliva. In many animals, a process similar to insalivation takes place, while the food remains in the mouth. In several species of the ape tribe there is a pouch situated on each side of the jaw, and in these pouches the greater part of the food is retained, not merely as some suppose, to serve as a fùture meal, but to undergo a dilution by the fluids that are there secreted. In granivorous birds, the food is first received into a membranous bag, formed by a dilatation of the gullet, and commonly called the crop, where it is macerated by the fluids that are there separated by means of glands or exhaling vessels, and passes down, as the animal requires, to be further prepared by the stomach. The bustard, indeed, though a granivorous bird, has no proper crop, but the gullet is furnished with numerous and large glands.

For an account of the chemical nature and properties of saliva, see CHEMISTRY, N° 2723.

The operation of deglutition depends chiefly on the Degluti action of the tongue, and on that of the muscles which tion. surround the pharynx and gullet. It is more or less speedy in proportion as these are more or less active and vigorous. Most animals, after having once swallowed their food, do not receive it again into the mouth; but this takes place in several tribes, and is called rumination, or chewing the cud.

Rumination takes place chiefly in those animals that Romina feed on herbage, and have not a muscular stomach; sucht.on. as all the tribes that Linnæus has ranked under the order pecora. In these the food, after being slightly chewed, is received into the first stomach, and after remaining there for a short time, it is gradually brought by a retrograde action of the gullet into the mouth, where it undergoes a complete trituration and insaliva

tion,

of tion, and is then conveyed into the 2d, 3d, and 4th Digestion. stomachs, to be mixed with the gastric juice.

159 Chymilication.

160 Organic action of the stomach.

Some of those birds which have a diluting sac or ingluvies, seem likewise to ruminate. This in the parrot was observed by the gentlemen of the French academy. It has since been observed in rooks, macaws, cockatoos, and others and Mr Hunter, to whom physiology is so much indebted, discovered that the male and the female pigeon secrete in their ingluvies a certain liquor for feeding their young; and that most kinds of what have been thought ruminating birds do very often in expressing their fondness regurgitate their food. Yet both this and another species of regurgitation which is very common with those animals that swallow indigestible substances with their food, should be carefully distinguished from rumination. For a farther account of rumination, and of the digestive organs of ruminating animals, see Comparative ANATOMY, N° 228-234. and Phil. Trans. 1807, Part ii.

The food having entered the stomach, undergoes in that organ processes that are partly mechanical, or rather organic, and partly chemical, depending on the structure of the stomach, and the nature of the juices secreted into its cavity. By these actions it is reduced into a pulpy substance commonly called chyme.

The organic action of the stomach is greater or less, according as this organ is more or less muscular. There are many animals, chiefly birds of the granivorous tribes, that have a very muscular stomach, commonly called gizzard, capable of grinding, not only the grains received into it, but even of reducing to powder small pieces of glass, and of blunting the points of needles and lancets. These facts were first proved by Borelli, who introduced into the gizzards of fowls, nuts, filberts, hollow spheres of glass, hollow cubes of lead, small pyramids of wood, and several other substances, which he found were either crushed together, or broken to pieces. He computes the power exerted by the stomach of the Indian cock as equal to the pressure of 1350 pounds weight. These experiments were repeated and verified by Spallanzani.

Some animals that are not possessed of a muscular stomach have, within that organ, teeth, or other hard bodies, for the purpose of breaking or grinding their food. This is the case with many of the crustacea, as crabs and lobsters.

A great many animals have what Spallanzani calls intermediate stomachs, i. e. not so muscular as the gizzard of fowls, nor so membranous as the stomachs of ruminating animals; this is the case with many birds, as ravens, crows, herons, &c. The stomachs of these animals are possessed of considerable force, though this is not nearly equal to that exerted by the gizzard. These animals possess the power of rejecting by the mouth the substances that are incapable of digestion in the stomach, every nine, or sometimes every three hours.

The animals with membranous stomachs are very numerous, comprehending man, most beasts and birds of prey; many reptiles, snakes, fish, &c. The stomachs of these animals are susceptible of but little muscular action, though in many species they both contract upon the food, and reject it through the gullet, on various occasions. Birds of prey, like the ravens, crows, &c. possess the power of rejecting, in the form of pellets, the

Of Digestion.

161

indigestible parts of their food, which usually takes place Every 24 hours. A most interesting paper by Mr Everard Home is published in the Philosophical Transactions for 1807, Discoveries part ii. on the structure and functions of the stomachs of various animals. We regret that we can here give Home. little more than the results of his inquiries.

From previous investigations respecting the stomachs of ruminating animals, Mr Home was led to believe that the fourth stomach in these tribes was either always, or during digestion, divided into two portions, each performing a different office in the digestive process; and he even conjectured, that a similar division might take place in other animals.

Mr Home has examined the stomachs of a great variety of animals, and investigated the progress of digestion in ruminants, the hare tribe, which occasionally ruminate, the beaver, dormouse, water-rat, common rat, mouse, horse, and ass, kangaroo, pecaré, hippopotamus, elephant, the cetacea, fowls, and lastly in man.

of Mr

162

link be

The human stomach appears to be the uniting link Human sto between those that are fitted only to digest vegetable mach the substances, and those of animals that are entirely car- tween carnivorous; and yet we find, that in its internal structure nivorous it is in every material respect similar both to those of and phitithe monkey and squirrel, which usually digest only ve- vorous sto getable food, and to those of carnivorous animals. 163

machs.

The human stomach is occasionally divided into a Into a carcardiac and a pyloric portion, by a muscular contrac-diac and tion similar to those of other animals; and as this cir-pyloric porcumstance has not before been noticed, it is proper to tion. be more particular in describing it.

The first instance in which Mr Home observed this muscular contraction in the human stomach, was in a woman who died in consequence of being burnt, and who had been unable to take much nourishment for several days before her death. The stomach was found empty, and was taken out of the body at a very early period after death. It was carefully inverted to expose its internal surface, and gently distended with air. The contraction was so permanent, that after the stomach had been kept in water, in an inverted state, for several days, and at different times distended with air, the appearance was not altogether destroyed.

Since that time, Mr Home has taken every opportunity of examining the human stomach shortly after death; and he finds that this contraction, in a greater or less degree, is very generally met with. He is of opinion that this effect is not produced by a peculiar band of muscular fibres, but that it arises from the mus cular coat, in the middle part of the stomach, being thrown into action to a greater or less extent according to circumstances. When this part of the stomach is examined by dissection, its muscular fibres are not to be distinguished from the rest. If the body be examined. so late as 24 hours after death, this appearance is rarely met with; a circumstance which accounts for its not having before been particularly noticed.

are

164

That the food is dissolved in the cardiac portion of Food first the human stomach, is proved by this part only being dissolved in found digested after death; the instances of which sufficiently numerous to require no addition being made to them. This could not take place unless the solvent liquor was deposited there. Mr Hunter goes so far as

the cardiac portion;

to..