temperature is no longer the same as in the living body. The bile may be stated to be a fluid containing water, with salts in solution, some common animal principles, and others peculiar to itself. The salts are compounds of the following acids:-colic acid, peculiar to the bile; margaric, oleic, acetic, carbonic, sulphuric, muriatic, and phosphoric, combined with soda; the last is also united with a little lime. To the carbonate of soda the bile owes its alkaline property, and hence it is sometimes used for the purpose of cleansing. The common animal principles are mucus derived from the lining membrane of the gall ducts, a modification of albumen, and osmazome. The peculiar principles are a yellow colouring matter, resin, and a substance, the taste of which is first sweet and then bitter, hence named picromel; but, when pure, it is sweet without bitterness, the latter quality being owing to the bile which it holds in solution, and for which it serves as a solvent. Besides, in the human bile another peculiar substance has been detected. From its forming the basis of, and giving consistence to, gall-stones, it is called cholesterine; in external appearance it very much resembles spermaceti. Later The Pancreas, or sweetbread, is an elongated gland, about five or six ounces in weight, lying in the curvatures of the duodenum, and presenting a structure very much resembling the salivary glands, whence it was inferred that it furnished a secretion similar to the saliva. examinations have shewn that the pancreatic fluid differs from that secretion in containing a considerable quantity of albumen, a curdy substance, and in the absence of sulpho-cyanic acid; the fluid secreted by the pancreas is collected by the branches of its duct, which terminates generally, in common with the bile duct, in the duodenum. The Spleen is a dark purple or livid-coloured body, weighing about eight ounces, situated in the left side, and attached to the stomach and some neighbouring parts. It is of a loose, spongy, and exceedingly soft texture, very abundantly supplied with blood-vessels, but has no ducts; nor does it appear to elaborate any peculiar secretion from the blood. The purpose it serves will hereafter be examined. The above engraving will give an idea of the general form and relative position of the different organs engaged in digestion:-a is the gullet; b, the stomach; c, the duodenum; d, the convolutions of the small intestine; e, the cœcum; f, the appendix of the coecum; g, the ascending colon; h, the transverse arch of the colon; i, the descending colon; j, the rectum; k, the liver; 7, the gall-bladder; m, the pancreas, the greater part of which is covered by the stomach; o, the spleen. In the en graving the liver is elevated, and the transverse arch of the colon drawn down, in order to shew parts which they cover in their natural position. When we consider the infinite variety of food on which animals subsist, we will be prepared to expect great diversities in the construction of the digestive organs. Yet it will be found that they are all formed upon the same general plan, from the highest to the lowest, though variously modified, so as to adapt them to the condition of each. It may be useful to advert to some of these modifications before entering upon the consideration of the action of the digestive apparatus, and the results of that action in the human subject. In those animals of the class mammalia which subsist upon flesh, such as the lion, the tiger, and the cat, the stomach is simple in its structure, the intestinal canal comparatively short, and the motions quick. The vascular distribution is also such as to admit of ready entrance of the new matter into the general system. On the other hand, in those which live upon crude vegetable food, such as grass, the digestive organs are complicated. In ruminating animals, as in the ox, sheep, deer, &c. there are four stomachs. The animal transmits the food into the first stomach without subjecting it to mastication in the first instance. This capacious cavity, known by the name of paunch, is of a somewhat globular form, lined internally with a dense insensible scarf skin, studded with numerous papillæ, and usually divided into distinct pouches by strong muscular bands. It exerts a rotatory motion, whereby, when indigestible substances, such as hair, are introduced, they are formed into round balls, as often occurs in oxen, from their licking their hides. It always contains a portion of the previous meals, for when the animal is even starved to death, a portion of food is still found in the paunch. This may be considered as a kind of cooking vessel; the food, on being introduced into it, is subjected to the internal heat of the animal, is brought in contact with that which for sometime has been under action, and kept in motion by the muscular power of this stomach. The second stomach is much smaller, and appears as an appendage to the first. It too is lined with insensible cuticle, and divided into numerous cells, generally of a hexagonal shape. It is termed the honeycomb, or king's hood. It appears chiefly to serve as a reservoir for fluids. In the camel and dromedary there are several pouches connected with this cavity, each capable of containing a considerable quantity of water. Their orifices are com manded by a sphincter muscle, whereby the water is retained without being contaminated with the adjacent food. These animals drink seldom, but take a large quantity at once, which is stored up for many days without undergoing change, remaining perfectly sweet and clean. We thus see how admirably they are constructed for traversing the arid deserts in which they are placed. The life of the traveller is occasionally preserved by his sacrificing that of his camel in order to procure the water contained in the cells of the honeycomb. The ruminant possesses a voluntary power over these two stomachs. When he chews the cud, a portion of food is detached from the general mass, probably a part of that which has been for the longest time lodged. As it passes the second stomach it receives a quantity of moisture, and is returned to the mouth, where it is subjected to trituration and insalivation. On being swallowed for the second time, by a curious power possessed over the gullet, it is transferred to the third cavity, which is the smallest of the four. Like the two former it is lined with cuticle, which is folded into broad plaits, from which circumstance it has obtained the name of many-plies. It has not been clearly ascertained what action the many-plies has upon the food; but that a certain chemical effect is produced, appears from the fact that here hydrogen gas is disengaged in considerable quantity. The fourth stomach is to be considered as the proper digestive organ; it is named the rennet. Internally the rennet is covered by a soft delicate mucous membrane, formed into longitudinal folds, and gastric juice is secreted in this compartment. In the suckling, the milk does not enter any of the three first, but, by a peculiar management of the gullet, it is immediately transferred into the fourth stomach, where it is curdled by the gastric juice, this being the first change to which it is subjected. power of coagulating milk possessed by the gastric juice is one of its most striking and remarkable properties. The rennet, even after being salted and dried, retains the power of imparting to water, on being infused in it, this quality; and accordingly that of the calf is prepared and preserved for this purpose in dairies. This The three first stomachs in ruminating animals may be held as merely subsidiary to the first, where the crude vegetable matter undergoes a process of preparation which may be compared to the effects of cooking, so as to render it more susceptible to the action of the proper stomach. Where, however, such influence is unnecessary, as in the case of milk, the food is not introduced into them, but directly conveyed into the fourth. Notwithstanding the length of time, and the extent and complexity of apparatus to which crude vegetable food is exposed in these animals, it is calculated to yield but a sparing quantity of nourishment. Accordingly, the intestinal canal is long and capacious, so as to afford both time and surface, that the whole of the nutritious portion may be taken up, and that every particle capable of furnishing nutriment may be abstracted. In monogastrics-that is, animals with a single stomach which subsist on vegetable food-various modifications of the digestive organs, so as to adapt them to their office, may be observed. The stomach is divided into two portions, especially during the process of digestion, the left extremity serving as a capacious reservoir where the food |