2G8 ROLLIN T. WOODYATT 



be found at times in association with diabetes when besides the true dia- 

 betes there are also the conditions responsible for these meliturias, e. g., 

 the ingestion of pentoses in the food, intestinal flora that liberate pentoses 

 from pentosans, diseases of the intestine and liver and other metabolic 

 anomalies, but there is no convincing evidence in the literature that the 

 occurrence of increased quantities of any sugar in the urine except glucose, 

 is consistently associated with diabetes or that it has any direct relation- 

 ship to this disease. 



Mechanism of Glycosuria 



Glucose is constantly being supplied to the tissues and constantly being 

 utilized. The primary factors to consider are: (1) The rate of glucose 

 supply, (2) the rate of glucose utilization. On their absolute values and 

 the ratio of (1) to (2) will depend variations of the level of free glucose 

 in the body. This level will also be influenced, theoretically, by a third 

 factor, (3) the rate of glucose excretion. Thus glycosuria might theoret- 

 ically be produced (a) by an abnormal increase of the raite of supply; (b) 

 by an abnormal retardation of utilization; (c) by a lowered threshold of 

 excretion provided that all other factors remained the same or provided 

 they did not change in such a way as to affect .one another. The character 

 of the glycosuria will differ in certain respects depending on the mechanism 

 involved. Increasing the rate of glucose supply in health increases the rate 

 of utilization. As Allen has said, the more glucose is given the more is 

 used. Within certain limits the rate of utilization appears to rise as fast or 

 nearly as fast as the rate of supply. However, this ceases to be true 

 when the rate of supply exceeds these limits. Utilization then lags and the 

 lag grows progressively greater the more the supply is increased. Hence 

 the higher the supply the greater the excretion absolutely and relatively. 

 But with a normal power of utilization it is not possible by feeding experi- 

 ments to produce anything approaching a quantitative excretion of all 

 the glucose supplied in excess of certain limits, nor by subcutaneous in- 

 jections nor by any method in which the supply rate is limited by the 

 rate of absorption. 



Diabetic Glycosuria. The curves of glucose excretion obtainable in 

 cases of severe stationary and uncomplicated diabetes are incompatible 

 with any conception except that of a failure to utilize a normal percentage 

 of the glucose supplied in excess of a certain limit. . A heavy glycosuria 

 due exclusively to an increased supply of glucose from endogenous sources 

 could not occur without an increased utilization of glucose which woul( 

 necessitate an increased metabolic rate and a high respiratory quotient. 

 Lusk showed a 20 per cent increase of the metabolism in normal 8 to 9 kg. 

 dogs following the administration of 50 grams of glucose by stomach. 

 Even so the dose was insufficient to cause glycosuria in the ordinary 



