If physiologists experience much difficulty in satisfactorily explaining all the phenomena of _chymification_ or _stomach-digestion_, the reflecting reader will not be surprised to learn that they are still more puzzled to account for those of chylification or _intestinal digestion_. The organs concerned in the latter are so deep-seated and inaccessible during life, that very few opportunities occur of obtaining accurate information on the subject; and, therefore, in what follows, I shall not enter into disputed or intricate details, but confine myself to such general views as are not contested, and as the reader may easily understand. Fortunately, ignorance of this branch of the inquiry is of less practical importance than if it extended to stomachic digestion also; because such is the harmony between all the parts of the system, that whatever conduces to the perfect accomplishment of the first stage of the process, _chymification_, is in so far equally conducive to the proper fulfilment of _chylification_ or intestinal digestion. The simple fact, indeed, of our having no _direct_ control over the process of chylification, and of our being able to modify it only by varying, through the medium of the stomach, the elements out of which chyle is to be formed and the mode in which they shall be digested, is a proof that, practically speaking, it is chiefly the laws or conditions of stomachic digestion which are intended to regulate our conduct; and that, in obeying them, we in reality obey also those of intestinal digestion. * * * * * The organs concerned in chylification are the _duodenum_, the _liver_, and the _pancreas_; but in order to avoid repetition, I shall, in describing the first, notice also the remainder of the intestine. The _intestine_ or _intestinal canal_, as represented in the subjoined figure, begins at the pyloric orifice of the stomach P, and after many windings and turnings, called _convolutions_ (from the Latin word _convolutus_, rolled or folded together), terminates in the _rectum_ or _straight gut_ Y, at the external orifice called the _anus_. Although continuous throughout its whole extent, the intestinal tube is nevertheless divided by anatomists into six portions, to each of which a different name is assigned: the distinction between some of these is more nominal than real, but it still continues to be made on account of its convenience. The first grand division is into the small and great intestines; the former beginning at the stomach, including all the convolutions marked RSSSS,--and the latter beginning at T, where the small intestine terminates, and including the large gut UUUUXYY, which surrounds, and is partly hidden by, the other bowels. [Illustration]