594 



METABOLISM, NUTRITION AND DIETETICS 



lism has also been investigated during long-continued hypnotic sleep 

 (Hoover and Sollmann). The results were very much the same as 

 in an ordinary starvation experiment. 



It might be supposed that if an animal was given as much nitrogen 

 in the food in the form of proteins as corresponded to its daily loss 

 of nitrogen during starvation, this loss would be entirely prevented 

 and nitrogenous equilibrium restored. The supposition would be 

 very far from the reality. If a dog of 30 kilos weight, which on 

 the tenth day of starvation excreted 11-4 grammes urea, had then 

 received a daily quantity of protein equivalent to this amount 

 that is to say, about 34 grammes of dry protein, or 175 grammes of 

 lean meat the excretion of nitrogen would at once have leaped 

 up to nearly double its starvation value. If the quantity of protein 

 in the diet was progressively increased, the output of urea would 

 increase along with it, but at an ever-slackening rate; and at length 

 a condition would be reached in which the income of nitrogen 

 exactly balanced the expenditure, and the animal neither lost nor 

 gained flesh. 



In an experiment of Voit's, for instance, the calculated loss of flesh 

 in a dog with no food at all was 190 grammes a day. The animal was 

 now fed on a gradually increasing diet of lean meat, with the following 

 result : 



The loss of nitrogen in the urine and faeces is what was measured. 

 Knowing the average composition of ' body-flesh ' (muscles, glands, 

 etc.), it is possible to translate results stated in terms of nitrogen into 

 results stated in terms of ' flesh.' Muscle contains approximately 

 3-4 per cent, of nitrogen. Here, with a diet of 480 grammes of meat, the 

 dog was still losing a little flesh; it would probably have required from 

 500 to 600 grammes for equilibrium. The results are graphically 

 represented in Fig. 201, p. 596. 



The quantity of protein food necessary for nitrogenous equili- 

 brium varies with the condition of the organism ; an emaciated body 

 requires less than a muscular and well-nourished body. The least 

 quantity which would suffice to maintain in nitrogenous equilibrium 

 the famous 35 kilo dog of Voit, even in very meagre condition, was 

 480 grammes of lean meat, corresponding to 16 grammes of nitrogen, 

 or 35 grammes of urea that is, about three times the daily loss 



