e manner just described.

[Illustration: Fig. 60.--Diagrammatic Scheme of Intestinal Absorption.

A, mesentery;
B, lacteals and mesentery glands;
C, veins of intestines;
R.C, receptacle of the chyle (receptaculum chyli);
P V, portal vein;
H V, hepatic veins;
S.V.C, superior vena cava;
R.A, right auricle of the heart;
I.V.C, inferior vena cava.
]

The inner surface of the small intestine also secretes a liquid called
intestinal juice, the precise functions of which are not known. The
chyme, thus acted upon by the different digestive fluids, resembles a
thick cream, and is now called chyle. The chyle is propelled along
the intestine by the worm-like contractions of its muscular walls. A
function of the bile, not yet mentioned, is to stimulate these movements,
and at the same time by its antiseptic properties to prevent putrefaction
of the contents of the intestine.

153. Digestion in the Large Intestines. Digestion does not occur to
any great extent in the large intestines. The food enters this portion of
the digestive canal through the ileo-caecal valve, and travels through it
slowly. Time is thus given for the fluid materials to be taken up by the
blood-vessels of the mucous membrane. The remains of the food now become
less fluid, and consist of undigested matter which has escaped the action
of the several digestive juices, or withstood their influence. Driven
onward by the contractions of the muscular walls, the refuse materials at
last reach the rectum, from which they are voluntarily expelled from the
body.

Absorption.

154. Absorption. While food remains within the alimentary canal it is as
much outside of the body, so far as nutrition is concerned, as if it had
never been taken inside. To be of any service the food must enter the
blood; it must be absorbed. The efficient agents in absorption are the
blood-vessels, the lacteals, and the lymphatics. The process through which
the nutritious material is fitted to enter the blood, is called
absorption. It is a process not confined, as we shall see, simply to the
alimentary canal, but one that is going on in every tissue.

The vessels by which the process of absorption is carried on are called
absorbents. The story, briefly told, is this: certain food materials
that have been prepared to enter the blood, filter through the mucous
membrane of the intestinal canal, and also the thin walls of minute
blood-vessels and lymphatics, and are