94 
COMPARATIVE ZOOLOGY. 
process by which fresh material is taken up and added to 
the blood: Veins, Lacteals, and Lymphatics. Only the | 
two former draw material from the alimentary canal. 
It is a general law that the food is absorbed as fast as 
it is dissolved, and, therefore, there is a constant loss in 
the passage down the canal. In the mouth and cesopha- 
gus, the absorption is slight ; 
but much of that which has 
yielded to the gastric juice, with most of the water, is 
greedily absorbed by the veins of the stomach, and made 
to join the current of blood which is rushing to the liver. 
Absorption by the veins also takes place from the skin 
and lungs. 
Medicinal or poisonous gases and liquids are 
readily introduced into the system by these channels. 
We have seen that the oily part of the food passes un- 
changed from the stomach into the small intestine, where, 
acted upon by the pancreatic juice, it is cut up into ex- 
tremely minute particles. 
Fie. 58.—Lacteal System of Mammal: a, 
descending aorta, or principal artery; 
b, thoracic duct; ¢, origin of lacteal 
vessels, g, in the walls of the intestine, 
d; e, mesentery, or membrane attach- 
ing the intestine to walls of the body; 
J, lacteal, or mesenteric, glands. 
These, and the remaining nu- 
tritive substances not taken 
up by the blood-vessels, enter 
the system in a roundabout 
way. A multitude of mi- 
croscopic tubes form a net- 
work in the walls of the in- 
testine, and even run into 
the little velvety eile with 
which the intestine is lined.” 
The villi, projecting into the 
digested food, like rootlets 
into the soil, absorb the 
chyle, which is immediately 
passed into the net-work of tubes, called Jacteals, from 
the milky character of the chyle which they convey, in 
Mammals. 
These lacteals unite into larger trunks, which 
lie in the mesentery (or membrane which suspends the in- 
testine to the back wall of the abdomen), and these pour 
