368 THE METABOLISM OF THE CARBOHYDRATES 



carbohydrates form the greater bulk of the food-stuffs undergoing 

 combustion in the organism this quotient is nearly 1 ; for a 

 monosaccharide contains within its own molecule sufficient 

 oxygen to oxidise all its hydrogen, and requires oxygen from 

 without only for the oxidation of its carbon. It contains oxygen 

 and hydrogen in the same proportion as they exist in water. 

 Now, when a certain volume of oxygen combines with carbon, 

 the volume of carbon dioxide gas thus formed is equal to that of 

 the oxygen used. The theoretical R. Q. on a carbohydrate diet 

 is, therefore, 1. 



In the case of fats and proteids, on the other hand, the mole- 

 cule contains relatively more hydrogen, so that, for its oxidation, 

 it requires oxygen for its hydrogen as well as its carbon ; the 

 volume of oxygen absorbed is therefore greater than the volume of 

 C0 2 produced, and hence the R. Q. is less than 1. As a matter 

 of fact, for fats the R. Q. is 0-707, and for proteids it is 0-8. On 

 examination of persons suffering from severe diabetes it has been 

 shown that R. Q. is about 0*7 even when dextrose is given in the 

 food (Magnus Levy 30 ). 1 



There can be no doubt, then, that the excess of dextrose in the 

 blood in diabetes is due to the organism having, to a greater or 

 less degree, lost the power of utilising the sugar. 



We have already stated that the end products of the meta- 

 bolism of dextrose are carbon dioxide and water. If we compare 

 the structural chemical formula of dextrose with that of the end 

 products in its metabolism, it will at once be evident that two 

 chemical processes must be called into play in the break-down of 

 the molecule, viz. a process of disruption and a process of oxida- 

 tion of the disrupted groups ; or, it may be that oxidation takes 

 place first, and that the oxidised groups are then split off. It is 

 possible, therefore, that the failure of either of these processes 

 might be the immediate cause of the want of break-down of 

 dextrose in the diabetic organism. Let us consider which of these 

 processes is really at fault. 



1 This fact alone merely shows that carbohydrates are not being oxidised ; but 

 such might result from the elimination of carbohydrates from the diet, as in 

 starvation, where a practically identical R. Q. is obtained. Magnus Levy ( 30 ) 

 has recently shown that the R. Q. during rest and hunger in severe diabetes lies 

 midway between what it would be were fat and the non-carbohydrate portion 

 of proteid the only substances undergoing oxidation in the organism. Had the 

 carbohydrate moiety of proteid been also oxidised, he shows that the R. Q. would 

 have been distinctly higher than what he actually found it to be. 



