WORK 115 



as such in the tissues, although this had been denied by Biedl and 

 Winterberg (64). Kovalevsky and Markevic'z support the hypothesis 

 of Salaskin, and state that the ammonia, which disappears, is taken 

 up by the tissues and fixed there in some loose combination. In 

 proof of this contention they show that, after the disappearance of 

 the ammonia from the blood, the ammonia content of the tissues is 

 increased. They found an increase in the ammonia content of the 

 liver, muscles, and intestine, but not of the kidney. The work of 

 Uschinski (404) in this connexion is of interest, as he has shown 

 that the tissues can take up from the blood, after injection, various 

 salts and sugars ; urea was also taken up. Even more interesting is 

 the recent work of Knoop (222) and Embden (118) showing that 

 ammonia can apparently be directly used in the tissues (liver?) in the 

 synthesis of amino acids. 



Nevertheless, the resynthesis of the nitrogen-containing part of the 

 protein, which is presumably catabolized during work, is extremely prob- 

 able. Such a reutilization of the tissue nitrogen must and does take 

 place during starvation, as certain tissues and organs, even when doing 

 steady work, as the heart, retain practically their original weight up 

 to the last (Voit, Chossat). This idea of a resynthesis of the locally 

 catabolized nitrogenous material taking place within the tissues, parti- 

 cularly the muscles, is by no means a new one. Hermann (190), in 

 1867, put forward the hypothesis that the protein in all probability 

 was decomposed into a nitrogen-containing part, which was reutilized 

 in some way, and a nitrogen-free part, which was burnt. He believed 

 further that an increased output of nitrogen took place only when 

 the work done was very prolonged and severe when an actual de- 

 struction of the muscle fibres was brought about. Ffltiger (328) has 

 also suggested that the protein molecule might break down into two 

 distinct parts, one containing the nitrogen, which might be reutilized 

 for the formation of new protein, and the other nitrogen-free, which 

 could be used to satisfy the dynamic needs. Verworn (" Textbook 

 of General Physiology ") supports such a view, believing that, under 

 certain circumstances, regeneration of the nitrogenous residues can take 

 place at the expense of other foodstuffs and oxygen. He maintains 

 that this economical use of the costly nitrogen is wholly in accord 

 with the other economies of nature. Cathcart (90) also carried ou - 

 some experiments to gain further light on this problem of resynthesis 

 It was found that creatine, a substance which is not present under 

 normal conditions in the urine, always appeared (see p. 98) during 



starvation. It was assumed that the appearance of this substance was 



8* 



