PRODUCTS 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 (01 
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 Kiihne 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. 
/3-peptone, 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 w r as 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 JS T eumeister, 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 atmiclalbumose. 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. 
-Bull. Soc. chim., Paris, 1S75, tome xxiii. pp. 161, 193, 216, 242, 385, 433 ; xxiv. pp. 
2, 145 ; Jahresb. ii. d. Fortsch/r. d. Thier-C'hem., Wiesbaden, 1875, Bd. v. S. 299. 
Schiitzenberger'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, Hoppe-SeyUrs Med.-chem. Uitiersuch., Berlin, 1871, S. 480; Krukenberg, 
Sitzungsb. d. Jenaisch. Gesellsch. f. Med. u. Naiwrw., 1886. 
4 Ztschr.f. Biol. Miinchen, 1890, Bd. xxvi. S. 57. 
5 Sidney Martin, Journ. Physiol., Cambridge and London, 1S85, vol. vi. p. 336. 
