420 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 



This is all easily accounted for on the supposition that a variable 

 fraction of the proteid molecule is easily attacked and broken off into 

 amido-acids by trypsin, but it is very difficult to explain on the sup- 

 position that the proteid molecule, early in the process of decomposition, 

 breaks up into two halves, of which one changes through the stages of 

 hemialbumose and hemipeptone into amido-acids, while the other, 

 passing through antialbumose, halts at antipeptone. 



Description of the products formed in the pancreatic digestion 

 of proteids. The products of tryptic digestion may be isolated most 

 easily by experimenting with fibrin, either by impregnating it with the 

 ferment, washing, and allowing it to digest in dilute sodium carbonate 

 solution, or by digesting with a purified pancreatic extract. The pro- 

 ducts present at different stages may be studied by removing at intervals 

 a portion of the digest, stopping the digestive process, by boiling and 

 then investigating the nature of the dissolved substances. 



Coagulable proteid. If the test portion be removed before complete solution, 

 or just on complete solution of the fibrin, it will be found to contain coagulahle 

 proteid ; on neutralising, part of this, being a globulin in character, is thrown 

 out of solution, and the remainder on making faintly acid and boiling. 1 



The deuteroalbumose of pancreatic digestion. If, after removal of the 

 coagulated proteid by filtration, the solution be now concentrated, deuteroalbu- 

 mose can be precipitated from it by sodium chloride and acetic acid, and shown, 

 by subjection to further action of trypsin, to be purely an anti-compound, or, 

 in other words, to contain nothing in its molecule decomposable by the action 

 of trypsin into amido-acids. This anti-deuteroalbumose, as already stated, is 

 the only albumose found in tryptic digestion, and it is only found in the earlier 

 stages. Another portion of the digest may be acidified, and the albumose 

 thrown out of solution by saturation with ammonium sulphate, after which the 

 presence of peptone in the filtrate may be shown, after dilution or dialysis, by 

 the usual tests. 



After some days of tryptic digestion, the digest contains no coagulable 

 proteid or albumose, but only antipeptone, and the simpler products formed 

 by more complete demolition of part of the proteid molecule (or of the hypo- 

 thetical hemi-moiety), such as the amido-acids. 



The peptone of tryptic digestion or antipeptone. The peptone or peptones 

 formed by the action of trypsin on proteids can best be obtained from a 

 pancreatic digest which has been allowed to proceed to completion by 

 repeated digestion during several days with trypsin and dilute sodium carbo- 

 nate solution. This solution is concentrated to a small volume and filtered 

 from the tyrosine, which separates out on cooling. The filtrate is saturated 

 with ammonium sulphate, with the precautions described under peptic diges- 

 tion, 2 and the ammonium sulphate is similarly removed. The antipeptone may 

 now be precipitated by the addition of phosphoinolybdic acid, the precipitate 

 decomposed by baryta water, and excess of barium removed by cautious 

 addition of dilute sulphuric acid. Finally, the solution is concentrated to a 

 syrup on a water bath, and dried in vacua over sulphuric acid. 3 



Antipeptone agrees very closely in composition and properties with a 

 monobasic organic acid (Fleischsaure) recently isolated by Siegfried 4 from 

 muscle extract, of the composition and molecular weight represented by the 



1 See pp. 405, 415. 2 See p. 411. 



3 Kiihne, Ztschr. f. BioL, Munchen, 1893, Bd. xxx. S. 1. 



4 Ber. d. Tc. sacks. Gesdlsch. d. Wissensch., Math.-phys. Cl., 1893, S. 485; Arch. f. 

 Anat. u. PhysioL, Leipzig. 1894, S. 401 ; Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. 

 xxi. S. 360. See also C. W. Rockwood. Arch. f. Anat. u. PhysioL, Leipzig, 1895, S. 1 ; 

 Balke u. H. S. Ide, Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxi. S. 380. 



