CHAPTER LXVI. 



ENDOTRYPTASE AND PHILOTHION. 



By Dr. M. HAHN ( 335) and Dr. LAFAR ( 336). 



335. Endotryptase. 



THE existence of a proteolytic enzyme in yeast was indicated by 

 the discoveries of several of the earliest workers, attention to the 

 subject being drawn more particularly to the phenomena occurring 

 in autofermentation (p. 543, vol. ii.). After it had been shown by 

 THENARD (I.), PASTEUR (XXXIV.), and DUCLAUX (XXXI.) that 

 yeast loses weight during fermentation, and especially becomes 

 poorer in nitrogen, LIEBIG (II.) discovered the presence of leucin 

 in water surrounding yeast that had been undergoing auto- 

 fermentation. BECHAMP (VII., VIII., X., XI.) and SCHTTTZEN- 

 BERGER (II.) were the first who learned to differentiate two 

 separate processes in autofermentation : one leading to the decom- 

 position of the carbohydrates into alcohol and carbon dioxide 

 and the other resulting in the decomposition of proteids and 

 therefore worthy to rank as an actual digestion process. Bechamp's 

 discovery of the hydrolysed proteids in the water used for washing 

 yeast led him to formulate a physiological theory of fermentation : 

 "In yeast, as in the case of all living organisms, we observe a 

 double series of phenomena. First the phenomena of nutrition 

 and assimilation induced by the presence of their foodstuffs (sugar, 

 nitrogenous substances, and mineral salts), these various sub- 

 stances entering the cells endosmotically and being there trans- 

 formed and utilised in the construction of tissues for the new-born 

 cells Side by side with these phenomena of nutrition, however, 

 but reversed, occur the phenomena of disassimilation, whereby the 

 tissues are transformed into excrementitious substances, which 

 are no longer beneficial to the life of the cell, and are ejected." 

 (He classes alcohol and carbon dioxide in this category.) More 

 recently, BOULLANGER (I.), BEIJERINCK (XXXI.), ARTARI (I.), 

 WEHMER (XII.), and especially WILL (XXXV.) have more closely 

 investigated the proteolytic processes in yeast cultures, after the 

 theory of the autodigestion (autolysis) of yeast has been firmly 

 established by SALKOWSKI (II.), by the digestion of yeast in 

 chloroform water (seep. 175, vol. ii.). M. HAHN (I.) succeeded 



548 



