THE TRANSPORTING SYSTEM OF THE BODY 261 



intestine. The fats are absorbed by a special set of tubes, 

 the lacteals, so called because their contents have a milky 

 appearance. The lacteals end in certain minute but numerous 

 projections in the small intestine known as villi. It is through 

 the walls of the villi that the emulsified fats are absorbed. 

 The contents of the lacteals empty into the thoracic duct, 

 a tube about as large as a goosequill which extends up through 

 the thorax and empties into the general circulation under the 

 left collar bone. The blood supply to the stomach and in- 

 testines does not return at once to the heart but flows into a 

 larger vein, the portal vein, which goes to the liver. Here it 

 again passes through a set of capillaries where much of its 

 carbohydrate food is withdrawn and stored in the form of 

 glycogen, a kind of animal starch. Glycogen is also found in 

 the muscles. 



222. Functions of the Blood. The digested food used by 

 the cells is carried to them by the plasma and by them built 

 up into new tissues or oxidized to produce energy. Since the 

 blood vessels form a closed system, the plasma, in order to 

 reach the cells, soaks out through the walls of the capillaries 

 into the spaces between the cells. In this condition it is 

 known as lymph. The lymph is carried back to the circula- 

 tion through tubes that empty into the right and left sub- 

 clavian veins near the throat. The red corpuscles act as car- 

 riers between the cells and the lungs, bringing oxygen to the 

 cells and carrying away the carbon dioxide produced in respira- 

 tion. They are able to do this by means of the red coloring 

 matter, or haemoglobin, which they contain. This substance 

 combines with both oxygen and carbon dioxide and absorbs 

 whichever is more abundant. The white corpuscles act some- 

 what like scavengers, wandering here and there and destroying 

 bacteria and other harmful matter wherever met. They have 

 a sort of slow movement of their own and can pass through the 

 walls of the capillaries in their search for employment. Here 



