A MANUAL OF PHYSIOLOGY 



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 easy to translate results stated in terms of nitrogen into 

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

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

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

 from 500 to 600 grammes for equilibrium. The results are graphi- 

 cally represented in Fig. 137. 



The quantity of proteid food necessary for nitrogenous 

 equilibrium 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 during starvation. From this lower limit up to 

 2,500 grammes of meat a day nitrogenous equilibrium 

 could always be attained, the animal putting on some flesh 

 at each increase of diet, until at length the whole 2,500 

 grammes were regularly used up in the twenty-four hours. 

 A further increase was only checked by digestive troubles. 

 A man, or at least a civilized man, can consume a much 

 smaller amount both absolutely and in proportion to the 

 body-weight. Rubner, with a body-weight of 72 kilos, was 

 able to digest and absorb over 1,400 grammes of lean meat: 

 Ranke, with about the same body-weight, could only use up 



