CLE. iVA GE THEOR Y OE PR0TE1D DIGESTION. 4 1 1 
the term hemialbumosg, as applied to the substance, or rather mixture 
of substances, described above, ought to have speedily disappeared; 
unfortunately it has not yel done so. 
Soon after this a valuable aid to the study of the albumoses was 
found in the discovery of Wenz, 1 that saturation with ammonium 
sulphate precipitated all albumoses from solution, while the peptones 
remained dissolved. Heynsius 2 first noticed the powerful action of 
ammonium sulphate as a proteid precipitant, but fell into error in 
thinking that it precipitated peptones as well. More careful experiments 
by Wenz, in Kuhne's laboratory, showed that it did not precipitate 
peptones, and so it was instituted as a means of separating albumoses 
and peptones. The statement, however, that saturation with ammonium 
sulphate totally precipitates albumoses and leaves peptones dissolved, 
can only be made with a certain reservation. Certain proteid sub- 
stances remain unprecipitated by saturation with ammonium sulphate, 
and these may conventionally be labelled peptones ; but it has been 
shown 3 that, in order to precipitate completely bodies which had 
been known as albumoses before the introduction of ammonium sul- 
phate, it is necessary to help the ammonium sulphate by saturating in 
dilute solution and with varying reaction. If these bodies had not 
been classed with the albumoses before Wenz's discovery, they would 
probably now be peptones ; so conventional and artificial as this is the 
proteid classification with which at present we are forced to be content. 
In little or nothing except unimportant physical differences are the 
albumoses and peptones distinct. If ammonium sulphate did not exist, it 
would be difficult to say how to draw a sharp line between them : 4 both 
classes of bodies give the same reaction to the biuret test, and both are 
diffusible, though the albumoses more slowly so than the peptones. 6 
Separation of albumoses and peptones. — The following is the method 
recommended by Kiihne 6 for separating albumoses from peptones: — 
The fluid containing the products of digestion is freed from albuminates 
and coagulable proteids in the usual manner, and then, when sufficiently diluted 
and of nearly neutral reaction, is saturated while boiling with ammonium 
sulphate, and separated on cooling from the excess of salt and precipitated 
albumose. The solution is again heated, and after it commences to boil it is 
made strongly alkaline by the addition of ammonia and ammonium carbonate, 
then again saturated with ammonium sulphate, and once more allowed to cool, 
when a second precipitation of albumose and excess of salt takes place. A 
third time heated, until the smell of ammonia disappears, it is once more 
saturated while warm and made decidedly acid in reaction by the addition of 
acetic acid, when, on cooling, a third and last precipitation of albumose takes 
place, and the filtered fluid is supposed to contain nothing proteid except 
peptone; amphopeptone if the original fluid was the result of gastric digestion. 
The albumoses can be obtained by dialysis and concentration from the united 
precipitates. 
1 Ztschr. f. Biol, Miinchen, 1886, Bd. xxii. S. 1. 
2 Arch. f. d. ges. Physiol., Bonn, 1884, Bd. xxxiv. S. 330. 
3 Kiihne, Ztschr. f. Biol., Miinchen, 1893, Bd. xxix. 
4 For a discussion of this point see Pekelharing. Arch. f. d. ges. Physiol., Bonn, 1880, 
Bd. xxii. S. 185; 1881, Bd. xxvi. S. 515 : Internal. BeUr. z. wissensch. Med. Fcstsehr. R. 
Virchow . . ., Berlin; Ztschr. f. Biol., Miinchen, 1891, Bd. xxviii. S. 567; Xeumeister, 
ibid., S. 361 ; Kiihne, ibid., S. 571. 
5 See Kiihne, Ztschr. f. Bid.. Miinchen, 1892, Bd. xxix. S. 20; Chittenden and 
Amerman, Journ. Physiol., Cambridge and London, 1893, vol. xiv. p. 
6 Loc. cit. 
