CHEMISTRY. 13 



brans, and brewers' grains, 1 per cent of HCl was as effective as 3; 

 but on the residues of umbelliferous seeds 2 per cent of HCl was con- 

 siderably more effective. 



The conclusion from the experiments was that Stutzer's method should 

 be modified so as to allow 500 cc. of the pepsin solution with 1 per cent 

 HCl to act on 2 gm. of substance for at least 48 hours, and in the case 

 of materials like the residue of umbelliferous seeds, which present an 

 unusual resistance to the solution, 72 or 84 hours. 



It will be remembered that Stutzer first proposed to digest with pep- 

 sin solution for 24 hours, and when it was found that the results were 

 lower than in digestion trials with animals he proposed to follow the 

 pepsin digestion with alkaline pancreas digestion. Experiments ^vere 

 made by the authors to determine whether the favorable action of the 

 pancreas solution was due to the soda it contained. In these the pep- 

 sin digestion was followed by digestion with alkaline pancreas solution 

 or with soda solution of equal strength. Excluding the residues of 

 umbelliferous seeds, it was found that, as a rule, when the Kiihn method 

 (mentioned above) was followed the action of the pancreas was appar- 

 ently due to the soda it contained. In the case of umbelliferous seed 

 resulues the results were irregular. 



Twenty-two digestion experiments were made with oxen to compare 

 the results of natural and artificial digestion, and to test the accuracy 

 of Pfeiffer's statement that animals digest more protein than is dis- 

 solved by digestion with pepsin alone.^ These experiments were with 

 hay and rice meal, cotton-seed meal, ground meal, or aniseed resi- 

 due; and the artificial- digestion was according to Kiihn's method. 

 They showed that Pfeiffer's conclusions were wrong. The protein 

 insoluble in i)epsin (by Kiihn's method) was all voided by the animals, 

 indicating that pei)sin dissolves all that can be digested by ruminants. 

 In the method of artificial digestion followed by Pfeiffer not all of the 

 pepsin-soluble protein was dissolved. In other experiment the feces 

 were digested with pepsin (Kiihn's method) and i>ancreas solutions, 

 and the food was submitted to like digestion. The amount of nitrogen 

 left undissolved by this digestion was greater in the feces than in the 

 food; in other words, this artificial digestion with pepsin and pan- 

 creas dissolved more protein than was actually taken out by natural 

 digestion and by subsequent treatment of the feces. If the nitrogen 

 dissolved from the food by alkaline pancreas was really digestible, 

 then it would have been taken up by the animal and the total amount 

 of pepsin-insoluble nitrogen would not have reappeared in the feces, as 

 was the case. Hence the conclusion from botli laboratory experiments 

 and experiments on animals is that when all of the pepsin-soluble nitro- 

 gen of a food is dissolved by artificial digestion, a further solution 

 by treatment with alkaline pancreas is not a true digestive action, but 

 is only a result of the solvent action of the soda added in the prepara- 



i Jour. Landw., 31, p. 22X, 



