UOW FOOD IS DIGESTED 71 
it is admitted either to the capillaries or to the lymphatic 
system. If collected by the capillaries the absorbed food 
is carried to the portal vein, 
thence to the liver and finally 
to the heart, into which it is 
poured with the blue blood 
brought in from all parts of 
the body. At this point the 
blood contains both nutriment 
and waste. That part of the 
absorbed food which entered 
into the lymphatic system is 
carried to the thoracic duct. 
and delivered into one of the 
main blood vessels. Lymph ViLut CELLS 
is blood without the red blood Section of intestine showing villi: 
The parts are: a, arteries; b, villi; 
corpuscles. It wanders to all  ¢. villi cut open to show lacteal (1), 
and blood tubes; d, glands; m, 
parts of the body, surrounds Ubcles Uy Voltns aad oe, wall: of 
all the cells of all the tissues 
and carries and leaves with the very kind of food they 
need most. 
13. How food is distributed.—After food enters the cir- 
culatory system it takes the regular course of the blood. 
In impure blood it is carried to the right auricle of the 
heart, then to the right ventricle. This in turn contracts 
and forces the blood into the lungs, where oxygen is 
taken on and carbonic acid gas and other impurities are 
given off. From the lungs the blood, now red and pure, 
passes into the left auricle, and thence into the left ven- 
tricle, from which it is forced into the aorta, and dis- 
tributed to all parts of the body. 
14. Respiration—When the impure blood passes 
through the lungs, carbonic acid gas and other impuri- 
ties are held back and in breathing are exhaled and 
