4S2 



PHYSIOLOGY. 



The fats are savers of proteids, as they are used before the proteids 

 are attacked in metabolism. 



Sugar and starch are converted into hexoses and these are trans- 

 formed and built up into glycogen. Fats are broken up into fatty 

 acids and glycerine, not changed, but used as fat. 



Zuntz finds that fat can be used for muscular work with as much 

 economy as either proteids or carbohydrates. In fact, with fat, slightly 

 less oxygen and energy was required to do work on fat diet than with 

 the others. 



The following table shows the results when resting and working 

 on a diet principally of fat or of a carbohydrate or of a proteid 

 (Leathes) : 



During fasting the fats from their storage places return to the 

 blood, to supply the needed fat. The liver first transfers the fat in 

 starvation from the subcutaneous tissue and the abdomen. This 

 transfer of fat to the liver only ensues if glycogen has vanished, and 

 it can be prevented if the animal is fed with substances which rapidly 

 form glycogen. This transfer of fat to the liver is a reserve which 

 meets any emergency call upon the cells of the body for fat, as in 

 violent exercise. The vascular liver can give fat to the blood much 

 more rapidly than the cells of adipose tissue in the subcutaneous tissue. 

 Hence the liver supplies glycogen and fat for the sudden needs of the 

 body. 



Hanriot has discovered a lipase in the blood which breaks up the 

 fat in the blood into fatty acid and glycerine and makes them soluble 

 in water, so that they can pass through the wall of the capillary to 

 the tissue. A lipase in the tissues also breaks up the fat, so it can 

 return to the blood. 



