98 THE PHYSIOLOGY OF PROTEIN METABOLISM 



cent, on the eighth day of the fast. The Freunds, although they 

 obtained so conspicuous a fall in the output of urea could not detect 

 any greater increase in the ammonia output than 2 per cent. If this 

 figure be correct, it is extremely difficult to explain the enormous fall 

 in the percentage output of urea which they observed. Brugsch found 

 in the urine of Succi on the twenty-ninth day of fasting a maximum 

 ammonia output of 3 5^3 per cent, of the total nitrogen. 



The Output of Creatine and Creatinine. 



The output of creatinine does not maintain the regularity which it 

 exhibits under normal conditions. The investigations of Benedict and 

 Diefendorf (60), Van Hoogenhuyze and Verploegh (201), Hawk (173) 

 and myself (89) show a decrease, which is more marked in some ex- 

 periments than in others. Thus, in Beaut6, this fall was quite definite, 

 whereas in the subjects of Hawk it was only slight. Accompanying 

 the creatinine output there is in starvation an output of creatine 

 (Cathcart, Benedict, Hawk and others). In my subject, the amount of 

 creatine excreted first rose, then fell slightly, and subsequently re- 

 mained more or less constant to the end of the fast. Hawk observed 

 the same course in one of his subjects, whereas in the other the creatine 

 excretion reached its maximum in the first day, and then steadily 

 fell. Benedict noted in his experiment that the output of creatine 

 gradually increased during the fast. If the combined output, creatinine 

 and creatine, be considered, there is no marked fall, although the general 

 tendency is towards a decrease. Hence the decreased creatinine out- 

 put is compensated for by the output of creatine. 



From a study of the relationship of the output of creatine nitrogen 

 to that of total nitrogen in the urine of the fasting bird, Noel Paton 

 (320) holds that light is thrown on the nature of the course of protein 

 metabolism in the muscles and other organs. He thinks that if the 

 muscle " flesh " catabolized as calculated from the creatine excreted be 

 greater than the total "flesh" disintegrated as calculated from the 

 total nitrogen eliminated, the conclusion may be drawn that there has 

 been a retention of some of the muscle protein nitrogen, due either to 

 resynthesis in the muscle or to transference to some more essential organ. 

 On the other hand, when the " flesh " catabolized, calculated from the 

 output of total nitrogen, exceeds that calculated from the output of 

 creatine, the stored nitrogen, i.e. the circulating, or surplus protein of 



