ioo THE PHYSIOLOGY OF PROTEIN METABOLISM 



than 25 per cent, of the total nitrogen output i.e. protein catabolized 

 could be accounted for on the basis of the creatine eliminated. Thus 

 in subject E. the amount of muscle protein catabolized, calculated from 

 the creatine output, was equivalent to an output of only 20*06 grms. 

 of nitrogen, whereas the actual output of total nitrogen was 86*44 grins. 

 He and his co-workers have found that the creatine content of muscle 

 may be decreased as much as 66 per cent, by fasting, with but slight 

 reduction in the total nitrogen content. They concluded, therefore, 

 that it may be logically inferred that part of the creatine had been re- 

 moved from muscular tissue which was still functioning in the body. 

 Unless future experimental results are more conclusively in favour of 

 such an inference, to my mind the more probable explanation of the 

 results will still be the partial catabolism of muscular tissue and the 

 reutilization of the creatine-free nitrogenous rest in synthetic processes 

 elsewhere. 



In this connexion two observations of Abderhalden are of interest. 

 Abderhalden, Bergell and Dorpinghaus (39), with the present methods 

 of analysis, could demonstrate no difference in chemical constitution 

 between the tissues obtained from a normal and from a fasting animal. 

 Abderhalden (4) also found distinct evidence of the retention of 

 nitrogen in the tissues of an animal during fasting, the retention not 

 being necessarily in the form of protein. He reached this conclusion 

 from the observation that if a fasting animal were given a large 

 amount of fluid there was a marked rise in the output of nitrogen. 

 This rise in the output of nitrogen might, of course, be due to in- 

 creased catabolism of protein due directly to the giving of the water, 

 but Abderhalden considered such an explanation as highly improb- 

 able. In support of his conclusion he cited some previous work carried 

 out by himself in conjunction with Block (24) on an alkaptonuric 

 patient. They gave a large quantity of water (5 litres) to the subject 

 of the experiment who was on a fixed diet. The output of total 

 nitrogen in the urine rose markedly but without any accompanying 

 rise in the output of homogentisic acid. From this constancy in the 

 homogentisic acid output Abderhalden concluded that the protein 

 metabolism as such was quite uninfluenced by the giving of water 

 and that the increased output of total nitrogen was due simply to the 

 washing out of " free " nitrogen probably end products from the 

 tissues. Hawk (174), on the other hand, found that the giving of four 

 and a half litres of water on two successive days to a man in nitrogen- 

 ous equilibrium brought about a rise in the output of nitrogen in the 

 urine on both days. As the output was greater on the first day than 



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