DIGESTION 397 



metabolic protein, but gives the maximum quantity that may be 

 present. Kuhn 1 has devised a method for estimating digestible 

 protein, by means of pepsin and hydrochloric acid. By experi- 

 ments on animals he has proved that the indigestible protein fed 

 (estimated according to this method) is exactly equal to the in- 

 digestible protein excreted. That is to say, the animal cannot 

 digest the protein found to be indigestible according to Kuhn's 



Fig. 83. Goats ready for digestion experiment. 

 North Carolina Station. 



method. The metabolic products in an excrement, then, cannot 

 be greater than the protein digested from it with pepsin-hydro- 

 chloric acid, though they may be less. 



As a result of 20 experiments, Kuhn found from 0.36 to 0.58 

 gm. of pepsin-soluble nitrogen in excrement from oxen, with an 

 average of 0.48 gm. for each 100 gm. of digested dry matter. 

 1 Landw. Versuchs-stat., 1894, p. 204. 



