DR. PAVY AND DIABETES 39 



many carefully planned scientific experiments and thousands of 

 stock-raisers' balance-sheets have proved ; there is also little 

 doubt at the present time, though the fact has been much 

 disputed in the past, that the reverse change may occur and 

 sugar take origin from fat. As broad facts these transformations 

 are established but the chemical steps which are traversed 

 during their occurrence are as yet illuminated only by the faint 

 light of tentative researches. At one time, as I have already 

 pointed out, Pavy believed that a large portion, if not the whole, 

 of the carbohydrate eaten took this path of conversion into fat. 

 Later, like most others, he saw in the conversion a means of 

 disposing of carbohydrate in excess of current needs, by which 

 it could be stored for future use in a more stable form than 

 glycogen presents. 



In disease, errors of metabolism may lead to an arrest of 

 this conversion simultaneously with an arrest in the utilisation 

 of sugar. This combination is found in ordinary severe diabetes 

 attended with emaciation. On the other hand the ability to 

 turn sugar into fat may, temporarily at least, remain normal 

 while the power to burn sugar is lost, a state of affairs which 

 leads to pathological obesity and is, as it were, a kind of 

 "masked " diabetes. 



Only the younger school of chemical physiologists can be 

 said to have made any serious attempt to follow, in the body, 

 the molecular changes involved in this remarkable trans- 

 formation. Pavy, for instance, was preoccupied with other 

 aspects of the matter and was content, as we have seen, to let 

 his mind rest on the conception that the bioplasm of either the 

 intestinal-cell or the liver-cell takes up the sugar and gives 

 it out as fat. 



Modern experimental work has unfortunately given us no 

 more than probabilities concerning the actual stages of the 

 transformation. It is a noteworthy point, however, that such 

 work as has been done justifies the present tendency of 

 physiological thought to look upon the intermediate production 

 of substances of quite small molecular weight as essential to the 

 accomplishment of such profound changes. Instead of that 

 view of metabolism which conceives of one substance as losing 

 its molecular identity in some vague complex to emerge again 

 later as quite another substance, we tend to think rather of 

 definite molecular transformations occurring in successive 



