308 HUMAN PHYSIOLOGY 



It was once held that body fat could come only from 

 fat received in the food. This view was absolutely 

 disproved by a single argument on the part of the great 

 chemist Liebig. He called attention to the scant supply 

 of fat in the fodder of the cow as compared with the 

 large daily delivery of butter fat in the milk. No one 

 could maintain the old belief in the presence of these 

 facts. But Liebig merely showed that fat could come 

 from something other than itself, and it was not at once 

 decided whether proteins or carbohydrates were to be 

 regarded as the usual source. It may be said in antici- 

 pation of what is to come later that proteins are possible 

 fat-formers, but not generally so prominent as the carbo- 

 hydrates. 



The transformation of sugar to fat being a well- 

 established and frequent occurrence, it becomes natural 

 to inquire whether fat can be changed back again to 

 sugar. This seems easier from a chemical point of view 

 than the former reaction. But it has proved difficult to 

 demonstrate that it ever happens. There is at present a 

 difference of opinion in regard to it and it may well be 

 considered an open question. 



As was said of fat so it may be said of carbohydrate 

 that its essential service is performed when it is oxidized 

 with liberation of energy. There is a further cor- 

 respondence between the two in that the oxidation is 

 mainly effected in the skeletal muscles and that the 

 normal end-products are carbon dioxid and water. 



The Pancreas. The oxidation of dextrose stands in a 

 curious relationship to the normal activity of the 

 pancreas. We have dealt with that organ as a digestive 

 gland of great importance. We are now to see that it 

 has another function even more fundamental. About 

 the year 1889 certain investigators removed the pancreas 

 from dogs to observe the signs of deficiency which might 

 make their appearance. It would have been natural to 

 look for some loss of digestive capacity and a lowered 

 power to absorb food. Probably these results ensued 



