268 



ELEMENTARY PHYSIOLOGY 



liver before it flows through the hepatic vein into the 

 general venous system. But concerning both the pro- 

 cess of absorption itself and the changes undergone by 

 the absorbed products before they reach the heart, ready 

 to be distributed all over the body, we have probably 

 much yet to learn. 



Part II. — Food and NuTRiTioisr. 



1. Some Aspects of Nutrition.— Nutrition, on the 



statistical side, has also to deal with the (juantitative 

 relationships between tlie amount of food supplied and 

 the amount of waste excreted ; to strike a balance between 

 the two and to draw conclusions from the balance-sheet 

 as to how the business of the body is being carried on. 

 Further, since food not only repairs waste but also 

 provides energy, the balance-sheet must take into account 

 how much total energy is supplied in the food and 

 how this available income js expended as heat and 

 work. 



2. Some Statistics of Nutrition.— The average 

 weiglit of a healthy full-grown man may be taken as 70 

 kilogrammes (154 pounds). Such a body is made up, in 

 round numl)ers, as follows : — 



Muscles and Tendons 



Skeleton 



Skin 



Fat 



Brain 



Thoracic viscera 

 Abdominal viscera ... 

 Blood 



100 



