118 THE THEORETICAL VIEWS OF KUHNE. [BOOK II. 



Whilst pepsin in acid solution and under suitable conditions of 

 temperature, is able to convert a proteid into peptones, no further 

 decomposition of these peptones occurs however prolonged the action 

 of the artificial gastric juice, or however abundant the pepsin at 

 work. Trypsin in alkaline solutions, on the other hand, was found 

 by Ktihne to decompose proteids in such a manner that there re- 

 sulted, as final products of digestion, a quantity of peptone which 

 roughly amounted to half the weight of the proteid acted upon, 

 together with a mixture of much less complex bodies, of which the 

 best characterised were certain amido-acids, and particularly leucin 

 (amido-caproic acid) and tyrosin (oxy-phenyl-amido-propionic acid). 



Further, when the peptone resulting from the prolonged action of 

 an artificial gastric juice was subjected to the action of trypsin, this 

 enzyme was found capable of effecting the decomposition of a moiety, 

 but a moiety only, of the peptone, and this yielded the same pro- 

 ducts as would have resulted from the direct action of trypsin on the 

 original proteid. 



These interesting results led Kuhne to a surmise similar to that 

 to which Schutzenberger had arrived, and served as starting points 

 of several investigations which resulted in the conception, which we 

 owe to Kiihne, of the general lines upon which the decomposition of 

 a proteid proceeds under the influence of hydrolytic agents, however 

 diverse. 



To the peptone which resisted the action of trypsin, and which, 

 owing to this characteristic, he had no difficulty in separating from 

 the other products, Kiihne immediately assigned the name of 

 Antipeptone, whilst he assigned the name of Hemipeptone to a 

 hypothetical peptone which he believed to be associated with anti- 

 peptone in the mixed products of the action of pepsin and gastric 

 juice, and which yielded leucin and tyrosin when digested with 

 trypsin although he had not, as yet, been able to separate it 

 in a state of even approximate purity. To the mixed peptones 

 resulting from the decomposition of proteids by pepsin and acid, 

 Kiihne has, since then, assigned the name amphopeptones. 



The correctness of the surmise was, however, soon proved, and 

 Kiihne was able to describe the methods of preparing and separating, 

 in approximate purity, the hemipeptone of which he had predicted 

 the existence ; further by comparing the decomposition of proteids 

 under varied hydrolytic conditions, alone and in association with 

 Chittenden, he was able to discover several interesting products, occu- 

 pying an intermediate position between the native proteids and the 

 peptones. These researches are so full of interest, and a knowledge 

 of them is so essential to the investigator in all departments of 

 Physiological Chemistry, that a somewhat detailed exposition of 

 them is necessary 1 . 



1 The whole account which follows concerning albumoses and peptones is condensed 

 from the various elaborate memoirs published 011 the subject by Kiihne in association 



