CLEA VA GE THEOR Y OF PROTEID DIGESTION. 4 1 1 



the term hemialbumose, as applied to the substance, or rather mixture 

 of substances, described above, ought to have speedily disappeared; 

 unfortunately it has not yet 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 Kiihne'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. 5 



Separation of albumoses and peptones. The following is the method 

 recommended by Klihne 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.}, d. ges. PhysioL, Bonn, 1884, Bd. xxxiv. S. 330. 



8 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. Beitr. z. u-isscnsch. Med. Fcstschr. R. 

 Virchow . . ., Berlin; Ztsclir. f. Biol., Miinchen, 1891, Bd. xxviii. S. 567; Neumeister, 

 ibid., S. 361 ; Kiihne, ibid., S. 571. 



5 See Kiihne, Ztschr. f. Biol., Miinchen, 1892, Bd. xxix. S. 20; Chittenden and 

 Amerman, Journ. PhysioL, Cambridge and London, 1893, vol. xiv. p. 483. 



G Loc. cit. 



