Small and large intestines. _1, 1, 2, 2_.
Small intestine. _3_. Its termination in the
large intestine. _4_. Appendix vermiformis.
_5_. Caecum. _6_. Ascending colon.
_7_. Transverse colon. _8_. Descending colon.
_9_. Sigmoid flexure of colon. _10_. Rectum.]

The _Intestines_ are those convoluted portions of the alimentary canal
into which the food is received after being partially digested, and in
which the separation and absorption of the nutritive materials and the
removal of the residue take place. The coats of the intestines are
analogous to those of the stomach, and are, in fact, only extensions of
them. For convenience of description, the intestines may be divided into
the _small_ and the _large_. The small intestine is from twenty to
twenty-five feet in length, and consists of the Duodenum, Jejunum, and
Ileum. The _Duodenum_, so called because its length is equal to the
breadth of twelve fingers, is the first division of the small intestine.
If the mucous membrane of the duodenum be examined, it will be found
thrown into numerous folds, which are called _valvulæ conniventes_, the
chief function of which appears to be to retard the course of the
alimentary matter, and afford a larger surface for the accommodation of
the absorbent vessels. Numerous _villi_, minute thread-like projections,
will be found scattered over the surface of these folds, set side by
side, like the pile of velvet. Each _villus_ contains a net-work of
blood-vessels, and a lacteal tube, into which the ducts from the liver
and pancreas open, and pour their secretions to assist in the conversion
of the chyme into chyle. The _Jejunum_, so named because it is usually
found empty after death, is a continuation of the duodenum, and is that
portion of the alimentary canal in which the absorption of nutritive
matter is chiefly effected. The _Ileum_, which signifies something