Chap. XVI.] ALIMENTATION. 199 



the lacteal. The lacteals carry this fatty matter or chyle to 

 the larger lymphatics in the mesentery, and these empty their 

 contents into the thoracic duct which opens above into the great 

 veins on the riglit side of the neck. 



Thus the food in solution after passing through the liver, 

 and the emulsified food after passing through the lymphatics, 

 find their way into the right side of the heart. It is not to be 

 understood that matters in solution do not find their way into 

 the lacteals, nor, on occasion, emulsified fats into the blood- 

 vessels, but, broadly speaking, the food-products find their way 

 into the blood in the manner above described. 



Final destination of food-stuffs. — It is impossible to say defi- 

 nitely what becomes of the different food-principles after they 

 have once entered the current of the blood. In general, it may 

 be said that the carbohydrates are used for the production of 

 heat and work, and that the fats may be stored in the body and 

 used as fuel. The proteids do all that can be done by the fats 

 and carbohydrates, and, in addition, form the basis of blood, 

 muscles, and all the connective tissues. 



Still we cannot say that the carbohydrates perform a cer- 

 tain work in the body and nothing else, or that the pro- 

 teids and fats do. It is, however, generally understood that 

 the proteids, fats, and carbohydrates each do an individual 

 work of their own better than either of the others can do 

 it. They are also necessary in due proportion to the nutri- 

 tion of the body and work together as well as in their separate 

 functions. 



The body has always a store of material laid by for future 

 use. If this were not the case, a person deprived of food 

 would die immediately, as he does when deprived of oxygen. 

 The great reserve forces of the body are stored in the form 

 of adipose tissue and glycogen. The glycogen is given out 

 during the intervals of eating to supply material for heat 

 and energy; the adipose tissue is not so readily available, 

 but may be called upon during prolonged deprivation from 

 food. For a certain time the heat of the body may be main- 

 tained and work done on these substances, although no food 

 except water be taken. 



In conclusion we may say the food in the blood supplies the 

 wants of the body in five different ways : — 



