EDITORIAL, 3 



with alkaline pancreas solution after the pepsin digestion. He found 

 that when a digestive solution containing the pancreatic juice in proper 

 concentration and with the proper amount of alkali (soda) was allowed 

 to act directly upon the substance witbout previous treatment with 

 isepsin it dissolved practically the same amount as pepsin ; but when 

 allowed to act upon the residue from pepsin digestion it dissolved from 

 20 to 30 per cent more of the protein. Consequently he believed that 

 different groups of proteids were dissolved by pepsin and by pancreas, 

 and that for the digestion to be complete pancreas digestion must follow 

 the pepsin digestion. He described a method for artificial digestion in 

 which this order of treatment was followed. The fact that direct treat- 

 ment with pancreas dissolved practically the same amount as pepsin 

 would seem to be opposed to Stutzer's conclusion that the two digestive 

 solutions dissolved separate groups of proteids. 



Pfeiffer^ made further digestion trials in which he attempted to deter- 

 mine the metabolic; nitrogen in the feces by treating the latter with 

 pepsin solution. Taking this metabolic nitrogen into account, he found 

 that the artificial digestion with pepsin and pancreas agreed with the 

 natural digestion as closely as parallel experiments on animals. It was 

 then confidently believed that the utility of Stutzer's new method was 

 demonstrated, and that the method had been useful in calling atten- 

 tion to the error of determining digestibility by the natural method 

 without taking the metabolic nitrogen into account. Since this time 

 the metabolic nitrogen has frequently been taken account of in diges- 

 tion experiments on animals and has sometimes been a convenient 

 means of reconciling the differences between results on different ani- 

 mals. The investigations of Kiihn, which are now published, throw a 

 new light on the whole question. Kiihn found that digesting 2 gm. of 

 substance with 250 cc. of acid pepsin solution for 24 hours did not dis- 

 solve the total amount of pepsin- soluble nitrogen; but that to do this 

 500 cc. of pepsin solution must be used and the digestion continued for 

 at least 48 hours. In the case of some materials which resist the action 

 of pepsin solution, as the residues from the extraction of volatile oils 

 from the seeds of umbelliferous plants, the digestion should be con- 

 tinued for 72 or 84 hours. He found by laboratory experiments and by 

 experiments on animals that the action of the pancreas solution was 

 due wholly to the soda added in its prei)aration, and was not therefore 

 a true digestive process. The results of artificial digestion by his 

 method, i. e.. 500 cc. of pepsin solution acting for 48 hours, agreed well 

 with those by natural digestion; and the nitrogen dissolved from the 

 residue of the pepsin digestion by treatment with pancreas solution 

 was found to be indigestible to animals. Digestion with pepsin solution 

 in the manner described, without subsequent digestion with pancreas 

 solution, dissolved all of the protein of the feeding stuff" which could be 

 digested by animals. In the case of the residues from umbelliferous 

 seeds, which, as mentioned above, resist the action of the pepsin, 



1 Jour. Landw., H (1886), p. 425. 



