RETENTION OF PROTEID IN THE BODY 



123 



But, as appears in the table on the preceding page, with a sufficient excess 

 of calorific energy a considerable storage of proteid can be accomplished even 

 by the adult human body. 



From this we see that while an excess of nourishment is of first importance 

 for the retention of proteid, still other conditions are necessary. In adults, 

 especially, muscular activity exerts a very great influence which cannot be 

 explained solely by the greater supply of food which the working body de- 

 mands. This is evident from the following experiment by Caspari. 



A dog received a constant ration, containing 2,088-2,099 Cal. and 25.1 g. N 

 per day. During rest the N-balance for three days was 0.5, -|- 1.3, and 

 -f- 1.2 g. ; then followed a working period of four days with a daily N-balance of 

 1.4, 0.0, +0.1, +1.5 g. A period of rest inserted showed a N-balance of 

 + 1.3 g. ; whereupon the following five days at work gave + 2.5, + 3.7, + 2.9, 

 + 3.5, + 3.5 g. At the same time the animal fell off in weight during the first 

 working period from 33.0 to 32.6 kg., and in the second from 32.9 to 32.1 kg. In 

 this case there was no excess of nourishment, and yet a considerable quantity 

 of nitrogen was retained. 



To study more closely the conditions for the storage of proteid in the 

 growing body, and at the same time to exclude the influence of mere size, it 

 is necessary to compare the metabolism of two individuals of the same size, 

 one of which is grown and the other still growing. For this purpose Soxhlet 

 has brought together the results obtained by him on a suckling calf 50 kg. 

 in weight with those obtained by Henneberg on a grown sheep weighing 

 45.5 kg. 



From facts considered further back, we know that in the adult body the 

 rule is for the quantity of nitrogen excreted to agree very closely with the 

 quantity in the food. But, as the table shows, this is not true in the suckling 

 calf. Hence, it follows that the conditions for the combustion of proteid in 

 the growing body are much less favorable than in the adult body. And since 

 this difference cannot all be due to the greater absolute quantity of food 

 for the calf, we cannot choose but suppose that the cells of the growing organ- 

 ism possess a special ability to appropriate proteid from the fluids of the 

 body, and to convert it into protoplasm. More than this we do not know at 

 present. 



From facts obtained on the dog, concerning N-metabolism with a low 

 supply of N" in the food, the view has often been expressed that in order to 

 protect a store of proteid once obtained, as much proteid must be ingested as 

 was necessary to acquire it, or at least that the supply of calories must be as 

 great. But the experiments by Caspari mentioned above are opposed to this 



