Appearance of the Chyle in the small Intestines. 159 slowly carried along the small intestines, the viscid chyle adhering to the villi, and being detained in the furrows between the valvulæ conniventes; the excrementitious part finally reaching the colon. The chyle gradually disappears in its passage along the small intestines, being absorbed by vessels, which, with their contents, will be described in the following chapter. According to M. Majendie, there appear upon the contents of the duodenum, when derived from the digestion of animal or vegetable matter containing fat or oil, irregular filaments, sometimes flattened, sometimes rounded, which attach themselves to the villi. But under other circumstances a viscid greyish substance is found, that forms a layer of greater or less thickness, which adheres to the mucous membrane, and seems to contain the elements of the chyle. The bile has probably a triple use; to assist directly in the production of the chyle; to excite the action of the bowels; while part like the urine may be essentially excrementitious, and blending with the refuse portion of the food may be thus conveniently got rid of. Mr. Brodie ascertained that when the ductus choledochus is tied in young cats, the formation of chyle is totally prevented. The production of chyme under these circumstances takes place in the stomach as usual; and the small intestines are found to contain a semifluid substance resembling the chyme found in the stomach; but it appears not to undergo the process of decomposition which commonly takes place in the duodenum. It is however found of a thicker consistence in proportion to the distance from the pylorus, and near the termination of the ileum there remains only a consistent substance differing in appearance from ordinary feces. 160 Influence of the Bile. M. Majendie has subsequently repeated this experiment upon adult animals, and found that few survived the operation: but in two cases, where the animals outlived the experiment for several days, white chyle was formed, and fecal matter produced but not of the usual colour. In these cases the animals had not become tinged with yellow, while in Mr. Brodie's experiments the animals became jaundiced, the tunica conjunctiva acquired a yellow colour, and bile was seen in the urinea. These contradictory results are exceedingly perplexing; as it is no less impossible to doubt the exactness of M. Majendie's observations than the fidelity of Mr. Brodie's. M. Majendie found on introducing a piece of raw flesh into the duodenum of a healthy dog, that in an hour it had been carried to the rectum, with no further change than a discoloration of its surface. Upon fixing a morsel of flesh in the small intestine with a thread, after the lapse of three hours it appeared to have lost about half its weight: the fibrin had been principally removed: what was left was entirely cellular, and remarkably fœtid. Gas obtained from the small intestines of criminals executed shortly after a repast was found by M. Chevreul to contain no oxygen. In the two first cases in the following table, the repast had preceded execution two hours: in the third, it had preceded death four hours. Carbonic Acid. Hydrogen. Nitrogen. 1st 24.39 + 55.53 + 20.08 8.85 = 100 "Quarterly Journal, vol. xxviii. p. 343. In the preceding section the appearances of the contents of the duodenum are described from Dr. Prout's researches upon the comparative produce of animal and vegetable food. The composition of the two sorts of chyme represented in a tabular view is the following. These results were obtained as follows: Water. The quantity of water present was ascertained by evaporating to dryness a known weight of each of the specimens upon a water-bath. Chymous Principle, &c. The proportion of this element was determined by adding acetic acid to a known quantity of the mass, and boiling them together for some time. The solid result thus obtained was then collected and dried as before. It consisted partly of a precipitate composed of the digested alimentary matter apparently combined with the gastric secretion, and partly of undissolved and excrementitious alimentary matter. Dr. Prout considered this as the chyme, in which the albuminous principle was not yet so completely formed or developed as to be recognized, mixed with excrementitious matter. Albuminous Matter, &c. After the above had been re M moved by filtration, prussiate of potash was added to the acetic solution, which in the chyme from vegetable food produced no precipitate, indicating the absence of albumen; but in the chyme from animal food, a copious precipitate was thus produced. The albuminous matter present in the latter appears to have been partly derived from the flesh on which the animal had been fed. Biliary Principle. Both chymes were found to contain this principle. It was separated by digesting alcohol on the dried residuum of the chyme. This took up the biliary principle, which was then obtained by driving off the alcohol. It possessed all the usual properties of this principle, except that it appeared to be less easily miscible with water than in its natural state, and to approach more nearly to the nature of a resin or adipocire, changes probably induced in it partly at least by the action of the alcohol. Vegetable Gluten? The chyme from vegetable food, which consisted of bread, yielded a portion of a principle soluble in acetic acid, and not precipitable by prussiate of potash or ammonia. Hence it was not albumen. It was precipitated by solution of potash, and possessed some other properties analogous to vegetable gluten. Saline matter. The salts were obtained by incineration, and consisted chiefly of the muriates, sulphates and phosphates, as is usual in animal matters. Insoluble residuum. This consisted chiefly in the vegetable chyme, of hairs, &c.; in the animal chyme partly of tendinous fibres ". Function of the Colon. 163 SECTION 5. Office of the Great Intestines. When the refuse portion of the aliment has entered the great intestine, its return into the ileum is prevented by the valvula coli, which is formed of two semilunar flaps containing muscular fibres a continuation seemingly of the small intestine for a short extent into the cavity of the colon. The changes which take place upon the matter introduced into the colon are a further absorption of its fluid parts and an admixture with the secretion of the bowel, from which the excrementitious substance derives its fecal odour which till then is wanting. By whatever means absorption takes place from the great intestine, it appears probable that much nourishment may be received through this channel. Injections of strong broth into the rectum frequently prove nutritious: the height to which fluids thus injected ascend in the bowel does not seem to have been ascertained. The difference of the gaseous contents of the great and small intestines consists in the absence of pure hydrogen from the former: in its place a somewhat smaller proportion of carburetted and sulphuretted hydrogen is found. I extract from Dr. Prout's inquiries the continuation of a tabular view of the contents of the alimentary canal in dogs fed upon vegetable and animal food, which will serve additionally to illustrate the changes produced in different parts of the great intestine. |