912 NUTRITION AND HEAT REGULATION. 



Phlarhizin Diabetes. Phlorhizin is a vegetable glucoside ob- 

 tained from the roots of certain trees e. g., apple, pear. When 

 injected into an animal it causes a glycosuria which is temporary, 

 but which may be renewed by repeated injections. Examination 

 of the blood in this case reveals the fact that the percentage of 

 sugar is not increased, so that the immediate cause of the glycosuria 

 is different from that responsible for the diabetes of man or of 

 animals without the pancreas. A satisfactory explanation of the 

 action of the phlorhizin has not yet been obtained, but it would 

 seem that the drug acts in some way upon the kidney itself that 

 is, the tissues of the body are probably still able to metabolize the 

 sugar, but the blood is continually depleted of this substance 

 through the kidney ; it leaks off through the kidney faster than it 

 can be utilized by the tissues. The evidence at hand seems to indi- 

 cate that the sugar (in part at least) exists in the blood in some 

 form of colloidal combination, and that under the influence of the 

 phlorhizin the kidney breaks up this combination and eliminates 

 the sugar.* 



From this brief description of the fate of the carbohydrate 

 in the body it is evident that its history as a food-stuff might 

 be considered conveniently under three heads, namely, its supply, 

 its storage, and its consumption. The supply is regulated by the 

 diet. In the usual diet carbohydrate constitutes the chief and 

 also the most variable factor. Its cheapness, its ease of digestion 

 and of consumption make it the most convenient and economical 

 source of energy to the body. When our energy needs are large, 

 as in muscular work, the carbohydrate portion of the diet is 

 increased; when the energy needs are small, as in a sedentary 

 life, the amount of carbohydrate is reduced. The storage of 

 carbohydrate in the body is provided for temporarily by the 

 glycogenetic function of the liver and the muscles. This function 

 may be deranged for a time by injuries to the central nervous 

 system or by hypersecretion of the adrenal glands or the hypophy- 

 sis, in which case hyperglycemia and glycosuria result. Or the 

 glycogenetic tissues may be inadequate to handle all the sugar 

 absorbed from the alimentary canal (alimentary glycosuria), 

 and in this case also there is a temporary hyperglycemia and 

 glycosuria. At the consumption end the amount of sugar de- 

 stroyed is controlled by the energy needs of the tissues, especially 

 of the muscles. Failure to destroy the sugar at this point brings 

 on also a hyperglycemia and glycosuria of a more serious nature. 



Our sugar-regulating mechanism in fact may prove inadequate 



* For more complete details and the literature, see Macleod, "The Metab- 

 olism of the Carbohydrates" in "Recent Advances in Physiology," London 

 and New York, 1906, and Lusk, "Ergebnisse d. Physiologic," 12, 315, 1912. 



