254 A. I. RINGER AXD EMIL J. BAUMAOT 



the kidney cells of different, individuals. Because this glucosuria is caused 

 by too rapid absorption of glucose from the alimentary canal, it is known as 

 alimentary glucosuria. 



Carbohydrate Tolerance. In the preceding chapters it was shown that 

 the body is capable of taking care of large quantities of carbohydrates 

 (glucose) 1, by storing it in the cells of the liver and muscles in the form 

 of a colloidal state glycogen; 2, by utilizing, i. e., oxidizing it in prefer- 

 ence to other foodstuffs ; 3, by converting it into fat. It was further shown 

 that these three factors tended to prevent the glucose from accumulating 

 in the blood above certain concentrations, at which it surpasses the kid- 

 ney threshold and forces the kidney cells to excrete the glucose in the 

 urine. 



The appearance of glucose in the urine in detectible quantities by 

 means of the ordinary reagents (Benedict's or Fehling's solutions) has 

 always been considered a sign that the individual has overtaxed the "car- 

 bohydrate tolerating" mechanism, and the amount of carbohydrate that 

 it takes to bring about this condition has been known as the limit of his 

 toleranca ( 



We shall see. later that there are 'a number of pathological conditions 

 which affect the carbohydrate tolerance of individuals and that the carbo- 

 hydrate tolerance is therefore utilized as a means of detecting these patho- 

 logical conditions. It is therefore of the utmost importance to have a clear 

 concept of all the factors that determine and that may influence the carbo- 

 hydrate tolerance of perfectly normal people. 



In the light of our present knowledge that glucosuria is the result of 

 hyperglucemia and that there exists a difference in the sensitiveness of the 

 kidneys of different individuals to glucose concentration in the blood, it 

 is advisable to eliminate this variable factor, and to determine the toler- 

 ance for carbohydrate on the basis of the blood sugar concentration. We 

 would therefore define the carbohydrate tolerance of an individual as 

 that amount .of carbohydrates (glucose) 8 which the individual can ingest 

 without developing hyperglucemia, and is in reality a test for the prompt- 

 ness with which the individual can convert glucose into glycogen and fat 

 and also oxidize it. 



Of course, one should not imply from the above that urinary examina- 

 tion for sugar is not necessary. It frequently does give valuable informa- 

 tion. 



Soon after the introduction of reliable methods for blood sugar de- 

 termination (Lewis-Benedict, Bang) a whote series of studies were pub- 

 lished on the blood sugar curves after the ingestion of variable amounts 

 of glucose (Hamman and Hirschman, 1917. Hopkins, 1915. Jacobson, 

 1913. Bailey, 1919). The most satisfactory results are obtained after 



'Glucose is used because this requires no time for digestion and thus another 

 possibly variable factor is eliminated. 



