454 PHYSIOLOGICAL CHEMISTRY. 



starvation (HIRSOHFELD). In conformity with this the animal 

 may be kept alive longer by food containing only non-nitrogenized 

 bodies than in complete starvation. 



The absence of fats and carbohydrates in the food affect car- 

 nivora and herbivora somewhat differently. It is unknown whether 

 carnivora can be kept alive for any length of time by food en- 

 tirely free from fat and carbohydrates. But it has been positively 

 demonstrated that they cannot only be kept alive by feeding entirely 

 with meat freed as much as possible from visible fat, but that flesh, 

 and perhaps also fat, is deposited. Men or herbivora, on the con- 

 trary, cannot live for any length of time on such food. On one 

 side they lose the property of digesting and assimilating the neces- 

 sarily large amounts of meat, and on the other a distaste for large 

 quantities of meat or proteids soon appears. 



III. Exchange of Material with Various Foods. 



For the carnivora, as above stated, meat as poor as possible in 

 fat may be a complete and sufficient food. As the proteids more- 

 over take a special place among the organic nutritive bodies by the 

 quantity of nitrogen they contain, it is proper that we first 

 describe the exchange of material with an entirely meat diet. 



Exchange of material with food rich in proteids, or feeding only 

 with meat as poor in fat as possible. 



By an increased supply of proteids the metabolization of pro- 

 teids and the elimination of nitrogen is increased and indeed in 

 proportion to the supply of proteids. 



If a certain quantity of meat is given as food daily to carnivora 

 and the ration of meat is suddenly increased, an increased metab- 

 olism of proteids or an increase in the quantity of nitrogen elim- 

 inated is the result. If we feed the animal daily for a certain time 

 with larger quantities of the same meat, we find that a part of the 

 proteids accumulates in the body, but this part decreases from day 

 to day, while there is a corresponding daily increase in the elimina- 

 tion of nitrogen. In this way a nitrogenous equilibrium is estab- 

 lished, that is, the total quantity of nitrogen eliminated is equal to 

 the quantity of nitrogen in the absorbed proteids or meat. If, on 

 the contrary, an animal which is in nitrogenous equilibrium having 



