38 PKOTE1DS. 



2>-peptone , not precipitated by strong nitric acid nor by potas- 

 sium ferrocyanide unless in presence of an excess of strong acetic 

 acid. 



e-peptone ; not precipitated by nitric acid nor by the potas- 

 sium salt, whatever be the amount of acetic acid simultaneously 

 added. 



These statements of Meissuer led to considerable subsequent 

 controversy, and the occurrence of the several products he de- 

 scribed was, with the exception of parapeptone and c-peptone, 

 denied by those who repeated his experiments. There is now 

 but slight reason for doubting that the divergent views are due 

 to the fact that Meissner's digestive extracts frequently contained 

 only small amounts of pepsin, while those of subsequent observers 

 were much more actively peptic, so that in their case several of 

 the intermediate products described by Meissuer were rapidly 

 peptonised and thus missed. Further it was urged that Meissner's 

 parapeptone was not a specific product of peptic action, for it was 

 said to be identical in all its chemical properties with ordinary 

 acid-albumin or syntonin Hence it was that Brucke, 1 opposing 

 Meissner, put forward the view, which has since been most gen- 

 erally accepted, that the sole products of a peptic digestion are 

 parapeptone and peptone, the former being due to the action of 

 the acid necessary for the activity of the pepsin, the latter making 

 its appearance as the sole final specific product of the ferment's 

 action on the first formed parapeptone, Schiff alone appears to 

 have supported Meissner. 2 



The researches of Kilhne. From what has been already said it 

 is at once evident that Meissner's view implied a decomposition 

 or splitting-up of the primary proteid molecule, inasmuch as he 

 held that his parapeptone was incapable of conversion into pep- 

 tone by the further action of pepsin Brucke on the other hand 

 regarded the process of peptonisation by gastric juice as not 

 necessarily involving any decomposition of the proteid molecule. 

 Kiihne, impressed with the profound and obvious decomposition 

 which trypsin brings about when it acts on proteids, reverted 

 once more to the possibilities implied in Meissner's views. In so 

 doing he found further confirmation of the idea that even in gas- 

 tric peptonisation the proteid is not merely changed but split up, 

 in the fact that only a portion of the gastric peptones can be 

 made to yield leucin and tyrosin by the action of trypsin ; from 

 which it follows that during a complete gastric peptonisation at 

 least two distinct peptones are formed. In accordance with this 

 he assumed that the original proteid molecule must itself consist 

 of two parts, of which each yielded its corresponding peptone 



1 Sitzb d. Wien. Akad. Bd. xxxvii. (1859), S. 131 ; XLIII. (1861), S. 601. 



2 Lecons sur la digestion, J867, T. i. p. 407 , u. p. 12. 



