CHAP. XV.] ALIMENTATION. 177 



Thus the food in solution finds its way into the right side of 

 the heart after passing through the liver, and the emulsified 

 food after passing through the lymphatics. 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 

 force, and that the fats are stored in the body and used as fuel. 

 The proteids do all that can be done by the fats and carbo- 

 hydrates, and, in addition, form the basis of blood, muscles, and 

 all the connective tissues. 



Still we cannot say that the carbohydrates perform a certain 

 work in the body and nothing else, or that the proteids 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 neces- 

 sary in due proportion to the nutrition 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 adi- 

 pose 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 maintained 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 : 



"1. It is used to form all the tissues of the body. 



" 2. It is used to repair the waste of all the tissues. 



" 3. It is stored in the body for future use. 



" 4. It is consumed as fuel to maintain the constant tempera- 

 ture which the body must always possess in a state of health. 



" 5. It produces muscular and nervous energy." (Professor 

 Atwater.) N 



