646 PHYSIOLOGICAL CHEMISTRY. 



sugar metabolism is so carefully controlled and is influenced by so 

 many factors that the details are not clear. The question has been 

 largely studied by observation of cases of spontaneous and experi- 

 mental diabetes. This term implies much more than a mere glyco- 

 suria ; hyperglucsemia (excessive amount of sugar in the blood) must 

 be present, and there is a profound change in the handling of carbo- 

 hydrates by the body, as well as some derangement of the protein and 

 fat metabolism. The pancreas plays an important role and furnishes 

 an internal secretion from the islands of Langerhans, which probably 

 enables the muscle to split and oxidize the glycogen as it needs it. 

 The muscle is thus involved, as well as the liver, in sugar control. 

 The adrenal is thought perhaps to control the transportation of sugar 

 in the body, for example, its removal from the liver to the muscle ; 

 while the thyroid seems to have an inhibitory action upon both the 

 pancreas and the adrenal. Phloridzin produces an increased perme- 

 ability of the kidney to sugar, but not a true diabetes. 



Fats. Shortly after the emulsified fats reach the blood through 

 the thoracic duct from the intestine, there occurs a peculiar change in 

 them whereby they become dialyzable, soluble in water, and insoluble 

 in ether. The nature of this change is entirely obscure. The fats 

 are deposited in the body as fats and form a reserve store of potential 

 energy. A small proportion is synthesized into the lecithins. While 

 the fat of any animal tends to remain true to the composition charac- 

 teristic of that animal, there is so little change in fat during digestion 

 that it is possible to recognize, in the tissue of the animal, foreign fats 

 which have been introduced with the food. The fat of the body is 

 derived primarily from the fat of the food, but is also formed in con- 

 siderable amount from carbohydrates. The location of this transfor- 

 mation of carbohydrate to fat is unknown. There is a possibility that 

 protein also may form fat, as it can undoubtedly form sugar, which 

 might be further changed to fat. Experiments in feeding foreign 

 fats have shown that the so-called fatty degenerations of the liver, 

 etc., are not transformations of protein into fat, but that the fat is 

 brought by the blood and deposited in the diseased organ. When fat 

 is burned it is first saponified. The final products are carbon dioxide 

 and water. The acetone bodies of the urine are believed to represent 

 steps in the incompleted oxidation of the fats. 



Proteins. After the proteins enter the portal blood as native pro- 

 teins they pass through the liver, probably with little change, and 

 are distributed to the tissues. Here a part enters into the repair or 

 the growth of the protein tissues (" tissue protein "), while a part is 



