820 NUTRITION AND HEAT REGULATION. 



may be the physiological cause of this peculiarity, there seems to be 

 no doubt that when used largely in the diet both animals and 

 men soon develop such an aversion to it that it is necessary to dis- 

 continue its use. A number of observers have attempted to de- 

 termine experimentally just how far the protein of the food may 

 be replaced by gelatin without causing a loss of body-protein. 

 Munk states, from experiments upon dogs, that when about six- 

 sevenths of the nitrogen necessary to maintain equilibrium was given 

 in the form of gelatin, the animal could be kept in nitrogen equilib- 

 rium for a few days at least. Kaufmann * kept himself in nitrogen 

 equilibrium for a short time upon a diet in which no protein was 

 contained, all the nitrogen being supplied in the form of gelatin 

 together with small amounts of the amino-acids which are lacking 

 in the gelatin molecule (cystin, tyrosin, tryptophan). 



* Kaufmann, "Pfliiger's Archiv f. d. ges. Physiol." 1905, cix., 440. 



