lae 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
rolled up, is the longest division of the small intestine. Although
somewhat thinner in texture than the jejunum, yet the difference is
scarcely perceptible. The large intestine is about five feet in length,
and is divided into the Caecum, Colon, and Rectum. The _Caecum_ is about
three inches in length. Between the large and the small intestine is a
valve, which prevents the return of excrementitious matter that has
passed into the large intestine. There is attached to the caecum an
appendage about the size of a goose-quill, and three inches in length,
termed the _appendix vermiformis_. The _Colon_ is that part of the large
intestine which extends from the caecum to the rectum, and which is
divided into three parts, distinguished as the ascending, the
transverse, and the descending.

[Illustration: Fig. 30.
Villi of the small intestine greatly
magnified.]

[Illustration: Fig. 31.
A section of the Ileum, turned inside out,
so as to show the appearance and arrangement
of the villi on an extended surface.]

The _Rectum_ is the terminus of the large intestine. The intestines are
abundantly supplied with blood-vessels. The arteries of the small
intestine are from fifteen to twenty in number. The large intestine is
furnished with three arteries, called the _colic arteries_. The
_ileo-colic artery_ sends branches to the lower part of the ileum, the
head of the colon, and the appendix vermiformis. The _right colic
artery_ forms arches, from which branches are distributed to the
ascending colon. The _colica media_ separates into two branches, one of
which is sent to the right portion of the transverse colon, the other to
the left. In its course,