materials.

[Fig. 76]


Fig. 76—*The villi.* _A._ Diagram of a small section of mucous membrane of
small intestine. 1. Villi. 2. Small glands, called _crypts_.

_B._ Diagram showing structure of villi. 1. Small artery. 2. Lacteal. 3.
Villus showing termination of the lacteal. 4. Villus showing capillaries.
5. Villus showing both the lacteal and the capillaries. 6. Small vein. 7.
Layer of epithelial cells.


*Work of Capillaries and Lacteals.*—The capillaries and lacteals act as
receivers of material as it passes through the layer of epithelial cells
covering the mucous membrane. The lacteals take up the digested fats,(66)
and the capillaries receive all the other kinds of nutrients. These
vessels do not, of course, retain the absorbed materials, but pass them
on. Their final destination is the general circulation, which they reach
by two well-defined channels, or routes.

*Routes to the Circulation.*—The two routes from the place of absorption
to the general circulation are as follows:

1. _Route taken by the Fat._—The fat is conveyed by the lacteals from the
villi to the receptacle of the chyle. At this place it mingles with the
lymph from the lower parts of the body, and with it passes through the
thoracic duct to the left subclavian vein. Here it enters the general
circulation. Thus, to reach the general circulation, the fat has to pass