PROD UCTS OF PEPTIC DIGESTION. 403 



albumate. If he had used a slightly stronger solution for a somewhat shorter 

 time, he would have obtained a mixture which would have been partially 

 peptonised and partially remained unchanged when subjected to the action 

 afterwards of strong fresh pepsin and acid ; if he had used a strongly peptic 

 solution for a much shorter time, the result would have been purely acid 

 albumin and no antialbumate whatever; giving with fresh pepsin, or more 

 prolonged action, complete peptonisation. 



On the addition of acid to the almost neutral faintly acid solution, a 

 further precipitate formed, which Meissner regarded as a different sub- 

 stance, and called metapeptone. It was insoluble in very dilute acids (O'l 

 per cent.), soluble in stronger acids. A third residue obtained in the diges- 

 tion of casein or fibrin he called dyspeptone ; this was insoluble in dilute 

 acids (2 per cent. HC1), but soluble in dilute alkalies and in stronger 

 acids. This substance was probably a mixture of nucleins, with the sub- 

 stance subsequently described by Klihne as antialbumid. 1 



After the removal of these neutralisation products, various other 

 substances were still left in solution ; these Meissner classed together 

 as peptones, distinguishing 



a-peptone, precipitable by concentrated nitric acid, as well as by potassium 

 ferrocyanide and dilute acetic acid. 



/?-peptoiie, not precipitated by nitric acid, but by potassium ferrocyanide 

 and strong acetic acid. 



y-peptone, not precipitated either by nitric acid or by potassium ferro- 

 cyanide and acetic acid. 



Of these three substances only y-peptone corresponds to the present-day 

 definition of a peptone the others were probably different albumoses. 



A valuable side-light was thrown on the digestion products of 

 proteids by Schiitzenberger's 2 researches on the prolonged action of 

 acids and alkalies at high temperatures on these substances. It has 

 already been indicated that peptonisation is the result obtained, 

 followed finally by a splitting up into amido-acids. 



Superheated steam possesses a similar peptonising action on proteids, and 

 yields by prolonged action the usual amido-acids. 3 According to Neumeister, 4 

 the intermediate substances produced are, however, somewhat different, the 

 substance first formed lies intermediate between the coagulable proteids and 

 the albumoses. It is not coagulated by boiling, but in its behaviour towards the 

 usual precipitants behaves like a coagulable proteid ; this substance is termed 

 atmidalbumin. By further hydration it yields a true albumose, which, however, 

 differs somewhat in its properties from any of the albumoses naturally formed 

 in digestion, and has been named atmidalbumose. Both atmidalbumin and 

 atmidalbumose are precipitated by dilute acids, and are converted by boiling 

 with dilute sulphuric acid into deutero-albumose. Similar products are pro- 

 duced by the action of the vegetable digestive ferment papoyotin or papain, 

 and are in the end, by the prolonged action of this ferment, converted into 

 amido-acids. 5 



1 See p. 406. 



2 Bull. Soc. chim., Paris, 1875, tome xxiii. pp. 161, 193, 216, 242, 385, 433 ; xxiv. pp. 

 2, 145 ; Jahr&b. u. d. Fortschr. d. Thier-Chem., Wiesbaden, 1875, Bd. v. S. 299. 

 Schutzenberger's researches are referred to at length in the article on the ' ' Chemical Con- 

 stituents of the Body," pp. 30-32 of this volume. 



3 Lubavin, Hoppc-Seyler's Med.-chem. Untersucli. , Berlin, 1871, S. 480; Krukenberg, 

 Sitzungsb. d. Jenaisch. Gesellsch. f. Med. u. Naturw., 1886. 



4 Ztschr. f. Blol. Miinchen, 1890,, Bd. xxvi. S. 57. 



5 Sidney Martin, Journ. Physiol., Cambridge and London, 1885, vol. vi. p. 336. 



