THE CARBOHYDRATES AND THEIR METABOLISM 255 



administering 100 grams of glucose dissolved in 400 c.c. of water to 

 which has been added the extract 1 or iy 2 lemons. This is to be taken 

 in the morning before breakfast. The blood is examined for sugar im- 

 mediately before the test meal, and at intervals of half hours after the 

 meal, until the blood sugar comes back to normal. 



With this procedure it* is found that most subjects have an initial fast- 

 ing blood sugar of 0.07 to 0.10 per cent; that about one hour after the 

 ingestion of the glucose the blood sugar reaches the highest point, which 

 is usually about 0.15 per cent or below; by the end of the second hour, it 

 is well on the way to normal again. 



If the individual's blood sugar rises above the level of 0.15 at any time 

 after the ingestion of 100 grams of glucose, we are justified in concluding 

 that he has interference, with his carbohydrate tolerance. A number of 

 records have been published on individuals classed as normal who show a 

 much higher blood sugar concentration one hour after glucose ingestion. 

 Future observations on the same individuals will reveal whether or not 

 they were normal. 



Carbohydrate Tolerance Standard. It is of no practical value to know 

 the maximum glucose tolerance of a person. But it is of great practical 

 importance to know that by far the great majority of hundreds of cases 

 of normal individuals who have received 100 grams of glucose have been 

 able to tolerate it, i. e., have shown no hyperglucemia and no glucosuria 

 when tested with the ordinary reagents. 



The setting of any physiological standard is difficult. We have, for 

 example, standard tables of weights. Are they in reality tables of what 

 we do weigh or of what we should weigh ? How many perfectly normal 

 human individuals actually bear the exact height to weight ratio? Still 

 we have accepted them as definite standards, realizing, of course, that 

 we may have plus or minus variations from the theoretical without being 

 classed as abnormal. 



The study of the carbohydrate tolerance of human individuals is of 

 comparatively recent development. And it will advance our science ma- 

 terially if those workers who reported hyperglucemias in what appeared 

 to be normal individuals will repeat their tests on the same individuals 

 at intervals of several years to see whether tRose people do not ultimately 

 develop glucosuria and diabetes. 



For persons weighing 60 kilos or more 100 grams of glucose should 

 be given. For those weighing less, the amount should be reduced pro- 

 portionately. But under no circumstances should more than 100 grams 

 be given to people weighing more than 60 kilos, because the increase in 

 weight is not so much due to muscle and liver (the glycogenetic organs) 

 as to fat and skeleton which play no role in carbohydrate tolerance. 



Glycogenesis and Carbohydrate Tolerance. While we have three out- 

 lets for the stabilization of the blood sugar concentrations, the most im- 



