Kiihne and Chittenden—Peptones. 243 
parently vigorous action of a poorly prepared gastric juice, or com- 
mercial preparation of pepsin and the action of solutions actually rich 
in pepsin. Even where the fibrin almost instantly disappears, the 
amount of ferment may still be quite insufficient to produce noticeable 
traces of peptones. Therefore care must be taken not to conclude 
immediately from a speedy solution, that digestion has been com- 
plete, since this is to be determined only by the disappearance of the 
primary cleavage products of digestion, that is, the change of albumose 
into peptones. 
It was especially interesting to ascertain whether peptones iso- 
lated according to the methods already described, were likewise pre- 
cipitated by ammonium sulphate or by other reagents that precipi- 
tate the albumose bodies, a question which was interesting considering 
the oft-asserted formation of albumin or albumose from peptones. 
To our surprise we noticed in the beginning that both antipep- 
tone and amphopeptone after complete purification, under certain 
circumstances gave rise to a turbidity or even a resinous precipitate, 
not only with ammonium sulphate, but also when their solutions were 
saturated with salt or when treated with acetic acid, nitric acid 
or metaphosphoric acid, just as if albumose had been formed or the 
albumose not completely removed by the previous treatment. Even 
if these precipitates concerned only a small part of the material in 
solution, their appearance would need explanation. So far as we can 
now determine, the occasion of this behavior is a circumstance con- 
cerning which we do not care to decide whether it really depends on 
the formation of albumose from peptone or not. It is to be ob- 
served that if the purification of the peptone by sulphuric acid is 
conducted incautiously, either on decomposing the barium-peptone or 
on acidifying before precipitation with phosphotungstic acid, the 
appearance afterward of albumose is avoided provided the solutions, 
when warm, are never exposed to an excess of acid. That a resinous 
precipitate appears, while boiling the solution saturated with ammo- 
nium sulphate at 110° C. has already been mentioned, but this can- 
not cause any impurity of the peptone remaining in solution, any 
more than the well known precipitation of antialbumid during trypsin 
digestion can occasion an impurity of the antipeptone. 
Since the fact is proved that peptones are not precipitated by am- 
monium sulphate, these bodies are then characterized more than ever 
by the property long attributed to them of being rendered turbid by 
very few reagents and completely precipitated by a still more lim- 
ited number. A list of the latter reagents includes only tannin 
