908 



PHYSIOLOGY 



hydrate and fat is shown in their influence on the excretion of creatine. 

 This substance is not present in normal urine, but almost invariably 

 makes its appearance during starvation. If carbohydrates be adminis- 

 tered after a period of starvation the creatine disappears from the 

 urine. On a pure diet of fat, however, as much creatine is found in 

 the urine as during complete starvation. These facts are well brought 

 out in the following Tables. Table I shows the effect of the administra- 

 tion of pure carbohydrate after a forty hours' fast. Table II shows 

 the effect of fat and of fat plus protein after a fast. In Table III the 

 fast was only relative, the diet during the first five days consisting 

 almost entirely of carbohydrates, during the next two days of almost 

 pure fat (cream), and on the last day an ordinary mixed diet. 



TABLE I 



Carbohydrate diet : 



Tapioca 454 grm. 



Sugar =114 

 Honey = 227 

 Cornflour = 85 



Calorie intake = 40 cal. per kilo. 



Carbohydrate in Fteces 

 19-0 grm. 

 4-5 



Cathcart concludes from these observations that the presence of 

 carbohydrates is essential for the utilisation of the protein given in the 

 diet. This conclusion is borne out by the results of feeding animals 

 with proteins which have been digested with pancreatic juice until 

 the biuret reaction has disappeared. After Loewi had shown that 

 it was possible to maintain nitrogenous equilibrium in dogs with such 

 a digest, Lesser was unable to confirm his results ; but it has been 

 pointed out that the essential difference between the two observers 

 was that Loewi gave an abundant supply of carbohydrates with the 

 digest, while Lesser omitted carbohydrates altogether and administered 

 fats and protein digest alone. 



The evidence that the carbohydrates play a necessary part in the 

 metabolic history of fats has already been mentioned, (v. p. 895). We 



