646 DIABETES 



excreted in diabetes is not always proportional to the concentration of sugar in the 

 blood, but is more nearly proportional to the product obtained by multiplying 

 the blood sugar percentage by a number representing the approximate blood volume 

 and other experiments to be described later point in the same direction. 



The Utilization of Sugar may be considered for present purposes as 

 the sum of the processes by which a sugar such as glucose is converted 

 into something else within the cells. In the case of glucose it includes 

 oxidation to yield finally CO2 and water; polymerizatio7i to yield a 

 series of substances, chief of which is glycogen; reduction to fat; 

 transformation, as to lactic acid; combination, etc. The rate of utili- 

 zation^ by all of these methods taken collectively is influenced in the 

 first place by the rate at which glucose molecules enter the cells and 

 secondly by the reaction conditions encountered within it. The 

 utilization rises with an increasing supply of glucose. As to the factors 

 which enter into what we have called the reaction conditions found 

 within the cell there is little definite knowledge. With a constant 

 glucose supply the rate of utilization may fall as the result of a defi- 

 ciency of that hypothetical substance derived from the pancreas. 

 It is well known that acid may retard glycogen formation and hasten 

 glycogen hydrolysis. It would appear from the work of Murlin and 

 Kramer'^ that alkali may increase glucose utilization. The rate of 

 actual oxidation is influenced by the supply of oxygen, etc. The fol- 

 lowing may serve to suggest other factors. 



It might be conceived that the cell contained molecules of a glucolytic catalyst 

 or enzyme similar in its effects to metallic hydroxides, that glucose molecules as 

 fast as they entered the cells would come into collision with catalyst molecules, 

 perhaps combining with them, and that as a result of the encounter the glucose 

 molecules would be dissociated into unsaturated fragments or ions. From the mo- 

 ment of union or dissociation they would cease to behave as glucose molecules. 

 The unsaturated fragments might subsequently suffer various fates, depending 

 upon the character and quantities of various substances in the cell. Thus, some 

 might combine with oxj^gen to yield, finally, carbon dioxide and water. Others 

 might combine with each other to form polymers like glycogen, others again 

 undergo reduction to fat or molecular rearrangement to give lactic acid. The 

 relative quantities undergoing those several changes, would depend upon the 



the larger tubes would not suffice to inject the smaller, while a rising pressure should 

 throw into action erstwhile empty collaterals and vice versa. A system of collateral 

 spillways would limit the distension of already filled capillaries and make the ac- 

 commodations of varying blood volume largely a matter of throwing in and cutting 

 out capillary cylinders. Such a method if followed exclusively woukl make the 

 surface rise faster than the volume, since the new clianncls would be of somewhat 

 smaller diameter. On the other hand, if a cai)illary wore cylindrical, increasing 

 its volume by increasing its diameter would lessen the ratio of surface to volume. 

 Increasing the volume of a cylinder by increasing its length would increase lateral 

 surface in proportion to volinne. Possibly in liealth, and within certain limits, 

 variation of the blood volume may cause proportional changes of capillarv surface. 



' Jour. Biol. Chem., 1914 (18), 21; Proc. Soc. Kxp. Biol., 1910 (13)" 07; also 

 "Studies in Hyperglycemia in Relation to Glycosuria," Albert A. Epstein, N. Y,, 

 1916. 



" It might not seem desirable to include such processes as temporary storage 

 in the form of glycogen under the heading of utilization. Tlie term is used for 

 convenience. 



' Jour. Biol. Chem., 1910 (27), 499. 



