DR. PAVY AND DIABETES 35 



which, however, the aldehyde group is intact and the group 

 (-CH 2 OH) oxidised- 



H H H H 

 O O O 



III! 



HOC — C — C — C — C — COOH 



I I I I 



H O 



H H H 



So too, he can oxidise saccharic acid — 



HOOC 



— from which both these groups are absent. Of these closely 

 related substances only sugar itself is not oxidised. 



These facts are in any case puzzling ; but with other facts 

 they make for the belief that what is absent in diabetes is not 

 an oxidative mechanism but a means to carry out a process 

 which, in the case of sugar, normally precedes oxidation in the 

 tissues. This process might be either a non-oxidative rupture 

 of the free molecule of sugar or it might be an event which 

 occurs while sugar is part of a complex. 



In connexion with the former possibility certain experimen- 

 tal work has been supposed to show that animal cells deal with 

 the sugar in the way that the yeast-cell deals with it — that the 

 primary change is alcoholic fermentation and that what is sub- 

 mitted to actual oxidation is the alcohol. More recent and 

 more critical experimental studies greatly diminish the proba- 

 bility of this rather startling suggestion. But we are left with 

 more solid ground for a belief in another form of cleavage or 

 rather for a cleavage stopping short at what is possibly the 

 precursor of alcohol in yeast fermentations. It is certain that 

 lactic acid is formed in animal tissues and there is a strong 

 probability that it is formed from carbohydrate. What evidence 

 we have concerning the significance of its appearance is almost 

 entirely derived from a study of muscle metabolism. 



In muscles lactic acid makes its appearance in appreciable 

 quantity only when the supply of oxygen is relatively de- 

 ficient. When such deficiency exists the acid appears in the 

 muscles of the living animal and is then, to some extent, excreted 



