374 THE METABOLISM OF THE CARBOHYDRATES 



acids separable from butter, and this increase was most marked 

 when butyric acid was given. Butyric acid is therefore un- 

 doubtedly one of the precursors of /3-oxy-butyric acid, &c. ; but it 

 cannot be the only one, for an amount of these substances is often 

 excreted far in excess of what could possibly be derived from this 

 source (vide Magnus Levy 30 ). The fact that Schwarz found the 

 non- volatile acids of butter (palmitic, stearic, and oleic) also to cause 

 an increase in their excretion further supports this contention. 



No experimental or clinical data throws any light on whether 

 only one oxy-butyric acid molecule is derived from each molecule 

 of these higher acids, or several. To answer this question it would 

 be necessary to know exactly how much fat is undergoing meta- 

 bolism in the body and how much oxy-butyric acid, aceto- acetic 

 acid, and acetone is meanwhile being excreted ; and, until this 

 question can be answered, it can scarcely be hoped that the exact 

 nature of the chemical process by which fat yields these bodies can 

 be understood. At present it is uncertain whether fat is alone 

 their source, or whether they may not be the products of some 

 synthetic process. 



The large amounts of sugar excreted in pancreatic and 

 phloridzin diabetes and in Diabetes mellitus cannot, as we have 

 seen, be derived entirely from the carbohydrates stored in the 

 body as glycogen. Where, then, does this excess of sugar come 

 from ? We have assumed, up to the present, that proteid must 

 be its source, and yet we have not proven beyond doubt that 

 such is actually the case, nor have we shown how, if this sugar 

 be so derived, the proteid comes to yield it : we have not, in 

 other words, explained the bio -chemical processes which must 

 ensue to bring about such a transmutation of proteid into car- 

 bohydrate. 



The discovery by Pavy that reducing bodies (sugars) are 

 formed when egg proteid is boiled for some time with mineral 

 acids, and the further chemical evidence along the same lines 

 which we have already considered, seemed to point to a pre-formed 

 carbohydrate group in the proteid molecule as the source of the 

 sugar. The evidence for, or against, such a derivation we shall 

 now consider in greater detail. 



We shall see whether fat at least the glycerine portion of it 

 may not contribute towards this sugar production in the body ; 



