MAINTENANCE REQUIREMENTS OF MATTER 317 



The facts recorded in Chapter VII (335-338), however, make 

 it evident that the protein katabolism may be affected by the 

 amount of both protein and non-nitrogenous material available 

 in the body. For a correct interpretation of the results of ex- 

 periments upon the maintenance requirement of protein, there- 

 fore, a knowledge of the influence of the feed supply upon the 

 protein katabolism is essential. 



402. Surplus protein katabolized. While a relatively small 

 quantity of digestible protein is sufficient, in the presence of an 

 abundant supply of fuel material, to maintain the body in 

 nitrogen equilibrium, an increase of the feed protein above 

 this minimum does not result in any large or long-continued 

 gain of protein tissue by the mature animal, but simply in- 

 creases the protein katabolism, as is shown by the prompt 

 appearance of a corresponding amount of nitrogen in the urine. 



TABLE 57. PROTEIN KATABOLISM OF SHEEP PER DAY AND HEAD 



The fact was demonstrated more than fifty years ago by C. Voit 

 in collaboration at first with Bischoff 1 and later alone and with Pet- 

 tenkofer 2 in experiments on carnivorous animals, and almost innu- 

 merable subsequent investigations have shown that it is true not 

 only of these animals but of man and of herbivorous animals as well. 



Of the -numerous investigations on herbivora in which the nitro- 



1 Gesetze der Ernahrung des Fleischfressers, 1860. 



2 Published chiefly in the Annalen der Chemie und Pharmacie and the Zeitschrift 

 fur Biologic. See also Voit, "Physiologic des Stoffwechsels," in Hermann's Hand- 

 buch der Physiologic. 



