Now all these foods, whatever be the degree of their putridity, are equally restored to a state of sweetness by the action of this juice, a short time after they have been introduced into the stomach.

Dr. Fordyce made a variety of experiments in reference to this subject upon the dog, and found uniformly that the most putrid meat he could be made to swallow, was in a very short time deprived of its putrescency. We cannot, therefore, be surprised that crows, vultures, and hyenas, who find a pleasure in tainted flesh, should fatten upon so impure a diet; nor that the dunghill should have its courtiers among insects as well as the flowergarden.

The gastric juice has hence been employed as an antiseptic out of the body, in a variety of cases.

Spallanzani has ascertained that the gastric juice of the crow and the dog will preserve veal and mutton perfectly sweet, and without consumption, thirty-seven days in winter; whilst the same meats immersed in water emit a fetid smell as early as the seventh day, and by the thirtieth are resolved into a state of most offensive liquidity.

Physicians and surgeons have equally availed themselves of this corrective quality, and have occasionally employed the gastric juice, internally in cases of indigestion from a debilitated stomach, and externally as a check to gangrenes, and a stimulus to impotent and indolent ulcers. I do not know that this practice has hitherto taken place very largely in our own country, but it has been extensively resorted to on the Continent, and especially in Switzerland and Italy; and in many cases with great success.

But the gastric juice is as remarkable for its solvent as for its antiputrescent property. Of this any industrious observer may satisfy himself by attending to the process of digestion in many of our most common animals; but it has been most strikingly exemplified in the experiments of Reaumur and Spallanzani. Pieces of the toughest meats, and of the most solid bones, inclosed in small perforated tin cases to guard against all muscular action, have been repeatedly thrust into the stomach of a buzzard: the meats were uniformly found diminished to three fourths of their bulk in the space of twenty-four hours, and reduced to slender threads; and the bones were wholly digested, either upon the first trial or a few repetitions of it. Dr. Stevens repeated the experiment on the human stomach by means of a perforated ivory ball, which he hired a person at Edinburgh alternately to swallow and disgorge, when a like effect was observed.

The gastric juice of the dog dissolves ivory itself and the enamel of the teeth; that of the hen has dissolved an onyx and diminished a Louis d'or* ; even among insects we find some tribes that fatten upon the fibrous parts of the roots of trees, and others upon metallic oxydes. And it is not long since that, upon examining the stomach and intestinal tube of a man who died in one of the public hospitals of this metropolis, and who had some years before swallowed a number of clasp-knives out of hardihood, their handles were found digested, and their blades blunted, though he had not been able to discharge them from his body.

* Swammerdam, Biblia Naturæ, p. 168.

It is in consequence of this wonderful power that the stomach is sometimes found in the extraordinary condition of digesting itself; and of exhibiting, when examined on dissection, various erosions in different parts of it, and especially towards the upper half, into which the gastric juice is supposed to flow most freely. It is the opinion of Mr. John Hunter*, however, whose opinions are always entitled to respect, that such a fact can never take place except in cases of sudden death, when the stomach is in full health, and the gastric juice, now just poured forth, is surrounded, by a dead organ. For he plausibly argues, that the moment the stomach begins to be diseased, it ceases to secrete this fluid, at least in a state of perfect activity; and that so long as it is itself alive, it is capable, by its living principle, of counteracting the effect of this solvent power. Yet a case has lately been published by Mr. Burns of Glasgow, in which the stomach appears to have been eroded, although the death, instead of being sudden, did not take place till after a long illness and great emaciation of the body. It is possible, however, that even here the stomach did not participate in the disease. That the living principle of the stomach is capable, so long as it continues in the stomach, of resisting the action of the gastric juice, can hardly be questioned. And it is to the superior power of this principle of life, that worms and the ova of insects are so often capable of existing in the stomach uninjured, and even of thriving in the midst of so destructible an agency.

*Phil. Trans. 1772.

But though the solvent juice of the stomach is the chief agent in the process of digestion, its muscular power contributes always something, and in many animals a considerable proportion, towards the general, result; and hence the shape and structure of this organ, instead of being uniformly alike, is varied with the most skilful attention to the nature of the mechanism by which it is to operate.

In its general construction, the stomach of different animals may be divided into three kinds ; membranous, muscular, and bony. The first is common to graminivorous quadrupeds, and to carnivorous animals of most kinds; to sheep, oxen, horses, dogs, and cats; eagles, falcons, snakes, frogs, newts, and the greater number of fishes, as well as to man himself. The second is common to graminivorous birds; and to granivorous animals of most kinds; to fowls, ducks, turkeys, geese, and pigeons. The third, to a few apterous insects, a few soft-bodied worms, and a few zoophytes; to the cancer genus, the cuttle-fish, the sea-hedgehog; tubipores and madrepores.

Of the membranous stomach we have already taken notice in describing that of man; and at the bony stomach we took a glance in a late lecture on the teeth and other masticatory organs. It only remains, therefore, that we make a few remarks on that singular variety of the membranous stomach which belongs to ruminant animals, and on the muscular stomach of granivorous and graminivorous birds.

All animals which ruminate must have more stomachs or ventricles than one; some have two,

some three; and the sheep and ox not less than four. The food is carried down directly into the first, which lies upon the left side, and is the largest of all; the vulgar name for this is the paunch. There are no wrinkles on its internal surface; but the food is considerably macerated in it by the force of its muscular coat, and the digestive secretions which are poured into it. Yet, in consequence of the vegetable and unanalogous nature of the food, it requires a much farther comminution; and is hence forced up by the œsophagus into the mouth, and a second time masticated; and this constitutes the act called rumination, or chewing the cud. After this process, it is sent down into the second ventricle, for the oesophagus opens equally into both, and the animal has a power of directing it to which soever it pleases. This ventricle is called the bonnet or king's hood; its internal surface contains a number of cells, and resembles a honey-comb; it macerates the food still farther; which is then protruded into the third ventricle, that, on account of its very numerous folds or wrinkles, is called manyplies, and vulgarly many-plus. It is here still farther elaborated, and is then sent into the fourth ventricle, which, on account of its colour, is called the red, and by the French le caillé, or the curdle, since it is here that the milk sucked by calves first assumes a curdled appearance. It is thus that the process of digestion is completed, and it is this compartment that constitutes the true stomach, to which the others are only vestibules.

There are some animals, however, which do not ruminate, that have more than one stomach; thus the hampster has two, the kangaroo three, and the