METABOLISM 207 



epithelium. There is some reason to believe that phloridzin 

 causes excretion of glucose in organs other than the kidneys. 



A rather rare condition known as renal diabetes is similar to 

 phloridzin diabetes in that sugar appears in the urine as a 

 result of a deranged condition of the kidneys. In this disorder 

 the level of blood sugar falls below normal, a fact which serves 

 to differentiate it from diabetes mellitus. The kidneys pour out 

 sugar into the urine even when blood sugar is at its normal 

 level, thus reducing it in amount. Evidently renal diabetes is 

 a disorder quite different in character from the ordinary type 

 of diabetes. 



Much speculation has been expended on the cause of diabetes 

 in man and its possible relationships to one or other of the forms 

 of experimental diabetes discussed, i.e., puncture diabetes, pan- 

 creatic diabetes or phloridzin diabetes. Obviously it is not 

 analogous to the last form, for the disease is accompanied by 

 increased sugar content of the blood. Clinicians generally are of 

 the opinion that it is closely allied to pancreatic diabetes. Evi- 

 dence, however, is not absolutely conclusive as yet, though it is 

 generally believed that lesions in the pancreas are usually if not 

 always the cause of the disorder. 



In the study of diabetes much use has been made of the so- 

 called assimilation limit for carbohydrates. A normal person 

 can take by mouth 300-400 grams of glucose, or even more 

 without the appearance of sugar in the urine. If sugar appears 

 in the urine after taking 100 grams of glucose, the subject is 

 considered to be diabetic. Woody at has suggested a new term, 

 sugar tolerance, based on the amount of glucose which can be 

 injected without causing glycosuria (sugar in the urine). He 

 reports that in the normal person 0.8-0.9 grams glucose per kilo 

 of body weight per hour can be used by the body. In a diabetic, 

 of course, the amount would be smaller than this, and if the 

 above mentioned amount is injected, sugar appears in the urine. 



A review of the foregoing discussion will emphasize the fact 

 that the internal factors regulating carbohydrate metabolism in 

 the body include a center in the medulla, presiding over the 



