490 KUHNE'S NEW METHOD OF PURIFYING PEPTONES. [BOOK n. 



IV. 



KUHNE'S NEW METHOD OF SEPARATING ALBUMOSES 

 FROM PEPTONES AND FOR THE PREPARATION OF THE 

 LATTER. 



(Supplementary to pages 136 and 137.) 



Since the sheet of this book in which the peptones were treated 

 of passed through the press, a very important paper by Kiihne has 

 appeared 1 , which is of so much importance in connection with the 

 mode of separation of the albumoses and peptones that the leading 

 facts which it contains must be referred to. 



All the other methods of preparing the peptones which result 

 from the action of pepsin and hydrochloric acid on the albuminous 

 substances (ampho-peptones), such as the methods of Henninger and 

 of Maly and Herth (described at page 136), yield, as products, mixtures 

 of albumoses with peptones in which the former preponderate. It 

 may indeed be positively asserted that until the appearance of the 

 paper under discussion no ampho-peptones had been obtained which 

 were free from albumoses. 



It is one of the fundamental and most important facts connected 

 with digestion by pepsin that, however active the solution of the 

 enzyme, however careful the experimenter may be in keeping up the 

 percentage of acid in the digestive mixture to the strength at which 

 proteolysis proceeds most rapidly under the most favourable con- 

 ditions of temperature (40 45 C.), however long the process may 

 go on (i.e. even though carried on for weeks and for months) large 

 quantities of albumoses are found mixed with peptones. 



After the publication of the paper of Wenz 2 , it was, at first, 

 believed that by simply saturating, in the cold, a mixed solution of 

 albumoses and peptones with ammonium sulphate, it was possible to 

 remove the whole of the albumoses from the solution, and Kuhne and 

 Chittenden's researches on peptones were all made on bodies purified 

 in thin manner 3 . Experiment however afterwards shewed that, in 

 order to effect anything like an apparently complete separation of 



1 W. Kiihne, ' Erfahrungen iiber Albumosen und Peptone, I. Keinigung der Peptone 

 von Albumosen,' Separatabdruck aus der Zeitschrift f. Biologie, 1893. 



2 Wenz, Zeitschrift f. Biologie, Vol. xxn. (1886), see p. 10. Eefer to pages 124 and 

 134 of the present volume. 



3 Kefer to page 137. 



