68 



Scientific Proceedings (72). 



may be determined by means of the hematocrit without resorting 

 to the use of a method which measures the total blood volume. 

 This is accomplished by establishing the changes that occur in 

 the proportion of cells in the blood from time to time and com- 

 puting therefrom, the alteration in the blood volume. 



Variations in the blood volume appear to be capable of affecting 

 the percentage relations of the different constituents of the blood, 

 including sugar. This circumstance necessitates a consideration 

 of the blood volume in the study of the sugar content of the blood; 

 for a change in the blood volume may alter the percentage con- 

 centration of the sugar and thus mask or modify an actual increase 

 or decrease in the amount of sugar present. Evidence is furnished 

 showing that the percentage of sugar in the blood may rise or fall, 

 as a result of change in the blood volume (bleeding, anesthesia, 

 sweating, ingestion of fluid), but the total amount may remain 

 unchanged. It is also shown that an increase in the total amount 

 of sugar may occur synchronously with an increase in the blood 

 volume (through dilution), causing little or no rise in the percentage 

 of sugar. 



In view of these facts it appears necessary to define hyper- 

 glycemia as an increase in the total amount of blood sugar over the 

 normal, and not merely an increase in concentration or percentage. 

 Thus it is possible to have a hyperglycemia even when the per- 

 centage of sugar is normal or below normal. 



The blood sugar is subject to very rapid changes. A single 

 examination of the blood sugar can not be used as a measure of 

 the sugar content for any period of time, no matter how brief. 

 Frequent estimations are therefore necessary, and the mean of 

 two or three estimations must be used to represent the probable 

 quantity of sugar in the blood for a given period of time. By 

 following this plan in the examination of the blood of diabetic and 

 non-diabetic individuals, it is found that the occurrence of gly- 

 cosuria is intimately connected with a hyperglycemia, i. e., an 

 increase in the total amount of sugar in the blood. 



In considering the quantitative relations between the glyco- 

 suria and the blood sugar in diabetes mellitus, the "hypergly- 

 cemia" is regarded as the sum of the greatest amount of sugar 

 that can be present in the blood without giving rise to glycosuria, 



