AGRICULTURAL EXPERIMENT STATION. 197 



belonging entirely to the undigested protein, and on the other, it 

 must be acknowledged that the treatment of the fodders with arti- 

 ficial digestive fluids is arbitrar}^ and may not correspond in the 

 extent of its action to that of the natural process of digestion. 



The most promising direction in which to look for an explanation 

 of widely different results for protein by the two methods seems to 

 be in a study of the nitrogen compounds of the feces. 



If by any means it is possible to separate the actual undigested 

 residue of protein from the other nitrogen compounds of the solid 

 excrement, we shall have a standard by which to judge artificial 

 methods of digestion, as well as a means of correcting the coeffi- 

 cient of digestibility for protein, as usually calculated, if such cor- 

 rection is necessar}^ 



Three methods have been tried for the separation of the biliary 

 and other waste products (stoffwechselproducte) from the real 

 undigested food residue, viz : (1) Successive treatment of the feces 

 with ether, alcohol and hot water; (2) the same followed by cold 

 lime water, and (3) digestion with a pepsin solution. 



The treatment with ether was the same as for a fat extraction, 

 and with the alcohol and water, 50 c. c. of each were used for each 

 gram of substance, the solvents being added cold, brought quickly 

 to the boiling point and kept at that temperature for about ten 

 minutes, filtered at once, and the residue washed with the same 

 liquid used for extraction. 



The treatment with lime water consisted in letting one gram of 

 the substance stand in 50 c. c. of a saturated solution for six houis 

 in cold. 



The pepsin solution was the same as that used in digestion of 

 fodders, the time of treatment beiijg twenty-four hours. The nitro- 

 gen was determined in the residues after extraction, and not in 

 solution. 



Determinations by two persons one using two grams of substance, 

 and the other one gram, gave practically the same results. 



Ill the table following can be seen the results of these different 

 mt thods of treatment. 



