FEEDING EXPERIMENTS WITH ABIURET PRODUCTS 39 



reaction had not disappeared, such a product could bring about nitro- 

 genous equilibrium. Abderhalden and Frank (36) put this observa- 

 tion to a further test. They completely hydrolysed horse flesh by 

 boiling with sulphuric acid and then added to the prepared products, 

 before feeding them to dogs, 0-5 per cent, tryptophane. They found 

 it was then possible to keep one dog in nitrogenous equilibrium for 

 twelve days and another for fourteen days. During these periods 

 the body weight remained fairly steady. E. Voit and Zisterer (411) 

 have worked out the actual relationship between undigested caseinogen 

 and caseinogen hydrolysed (a) by pancreatin, (b} by acid, as sources of 

 protein supply. Like other observers they found that " whole " casein- 

 ogen acted better than either of the hydrolysed products, and that 

 again the ferment digest was superior to the acid one. The ratio 

 between the three as sparers of protein worked out as follows : 



Caseinogen Caseinogen (Pancreatin) Caseinogen (Acid) 



100 107 127 



On the assumption that the work of Abderhalden and others was 

 correct they concluded that the acid hydrolytic products must be 

 accepted as more than protein sparers that such products, provided 

 they be not too fully hydrolysed, can take part in actual synthetic 

 processes. Like the majority of workers, they held that in gastro- 

 intestinal digestion there was a complete degradation of the food 

 protein to the simple amino acids or groups of these, and that certain 

 nuclei (probably polypeptide in nature) were absorbed unchanged. 

 It was with the help of these, and probably certain other nitrogen- 

 containing and nitrogen-free groups that the new protein was built up. 

 Abderhalden (5) also showed that it was impossible to prevent 

 tissue waste with caseinogen minus tryptophane. Three diets were 

 used (i) fully digested caseinogen, (2) fully digested caseinogen from 

 which the tryptophane had been removed, (3) fully digested case- 

 inogen from which the tryptophane had been removed and then the 

 proper amount again added. Nitrogenous equilibrium was obtained 

 with (i) and (3) but not with (2). In support of these experiments 

 are the further experiments of Abderhalden (3) in which he showed 

 that nitrogenous equilibrium could be obtained by the products of in- 

 complete acid hydrolysis. He used edestin partially hydrolysed by 

 treatment for five days at 20 C. with 70 per cent, sulphuric acid ; this 

 product consisted of curious polypeptide substances containing glutamic 

 acid, tryptophane and leucine. Similar results were obtained when 

 elastin, haemoglobin and keratin were treated in like manner. From 



