CHEMICAL BASIS OF THE ANIMAL BODY. 37 



6-peptone ; not precipitated by strong nitric acid nor by potassium 

 ferrocyanide unless in presence of an excess of strong acetic acid. 



c-peptone ; not precipitated by nitric acid nor by the potassium salt, 

 whatever be the amount of acetic acid simultaneously added. 



These statements of Meissner led to considerable subsequent contro- 

 versy, and the occurrence of the several products he described 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 Meissner 

 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 Briicke 1 , opposing 

 Meissner, put forward the view, which has since been most generally 

 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 Kuhne. 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 peptone by the further 

 action of pepsin. Briicke on the other hand regarded the process of 

 peptonisation by gastric juice as not necessarily involving any decompo- 

 sition of the proteid molecule. Kulme, 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 gastric 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 during the hydration 

 which leads to the formation of peptones 3 . He found also further 



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



2 Lecons sur la digestion, 1867, T. i. p. 407 ; n. p. 12. 



3 Verhandl. d. naturhist. -med. Ver. Heidelberg, N. F. Bd. i. (1876), S. 236. 



