THE PRECURSORS OF UREA 673 



probably due to a tissue ferment. Salaskin and Kowalesky have 

 shown that when glycin is injected into a systemic vein of a 

 dog, only a small part appears unaltered in the urine. The rest 

 soon disappears from the blood and is not to be found in the 

 tissues. And as the ammonia content of the blood is increased, 

 they suggest that the tissues have probably converted the glycin 

 into some ammonium compound. There are several pathological 

 conditions of the body in which mono-amino acids are excreted 

 in the urine. The best known of these is severe destruction of 

 the liver, such as occurs in the acute yellow atrophy of that 

 organ. But there are other more general conditions known in 

 which the same thing occurs, such as gout, phosphorus-poisoning, 

 pneumonia, and leucocythaemia. This suggests, like the experi- 

 ments of Lang, that the conversion of this amido-N into ammonia 

 is a property, not of a single tissue, the liver, but of the tissues 

 in general. 



(b) The Diamino- Acids. We know that they are formed from 

 proteid both by the digestive ferments and during the autolysis 

 of organs. We have but little information as to their fate in the 

 body, with the exception of arginin. More attention has been 

 paid to the possibility that their non-nitrogenous part may be 

 synthesised into a carbohydrate than to the fate of their nitrogen. 

 Mayer has experimented with diamino-propionic acid. He injected 

 it subcutaneously into a rabbit, and was able to demonstrate 

 small quantities of gly eerie acid in the urine. 



CH 2 .NH 2 CH 9 .OH 



I I 



CH . NH 9 + 2H,0 = CH . OH + 2NH 3 



I I 



COOH COOH 



This reaction entails the splitting off of amido-nitrogen as 

 ammonia, and this presumably would be converted into urea. 

 The reaction also illustrates the power the tissues have of 

 splitting of! the amido-nitrogen from comparatively complex 

 bodies without necessarily at the same time breaking up their 

 non-nitrogenous portions. Thompson has recently brought forward 

 proof that a diamino-acid is converted into urea in the body. 

 He fed dogs with arginin, and also injected it subcutaneously, and 



2u 



