ENDOTRYPTASE. 553 



powerfully decomposed, whilst in two cases out of three, pseudo- 

 globulin was left intact. 



With regard to the fission products resulting from the auto- 

 cligestion of yeast, the older statements must be accepted with a 

 certain degree of care, because it cannot always be safely deduced 

 from them that the putrefactive influence of bacteria was pre- 

 cluded ; whilst in some cases the method of experiment adopted 

 was such as might induce the decomposition of the proteids. Thus, 

 in their investigations on the chemical composition of yeast, 

 NlGELiand LOEW (II.) found 2 per cent, of peptones, which Loew 

 subdivided into a-, b- and c-peptone (Meissner). This result, 

 however, was obtained with an aqueous extract of yeast obtained 

 by eleven successive prolonged boilings, so that Nageli himself 

 was obliged to admit that the boiling water might have produced 

 hydrolysis. According to GERET and HAHN (I. and II.), albumoses 

 and peptone are not detected in expressed yeast juice digested at 

 37 C. ; and in fact, even when albumoses and peptone are added 

 to the juice, the biuret reaction soon disappears at a higher 

 temperature. On the other hand, when the digestion is retarded 

 by the temperature of the ice-chest, albumoses appear, these being 

 chiefly deuteroalbumoses, whereas true peptones, in the sense 

 indicated by Kiihne, cannot be identified. Moreover, since F. 

 KUTSCHER (III.) observed the occurrence of the biuret reaction 

 for a period of 814 days, during the digestion of yeast with 

 chloroform water: a process in which the enzyme only gradually 

 issues from the cells and comes into action the possibility of the 

 formation of small quantities of albumoses during the protracted 

 action of endotryptase must be admitted. Attention was also 

 directed, at an early date, to other fission products occurring in 

 the autodigestion of yeast. 'Thus, Liebig in 1868 referred to the 

 occurrence of leuchi during the aut of er mentation of yeast ; the 

 appearance of tyrosin among the fission products was observed by 

 Bechamp in 1872 ; and both workers contemporaneously noticed 

 a copious exudation of phosphoric acid from the yeast cell. Then 

 followed Schiitzenberger's discovery of butalanin, alloxuric bases, 

 carnin, sarkin, xanthin, and guanin (as well as tyrosin and leucin) 

 in the aqueous extract from self-fermenting yeast. This worker 

 regarded all these fission products as derivatives of albumen. 

 The experiments of KOSSEL (III.) and SALKOWSKI (II.) showed 

 that the phosphoric acid and alloxuric bases should be regarded 

 as fission products of the nuclein substances of the yeast cell, 

 whereas the leucin and tyrosin probably originate in the decom- 

 position of other proteids. This result is also confirmed by 

 the autodigestion of expressed yeast juice. Geret and Hahn 

 found that four-fifths to five-sixths of the phosphorus (mostly in 

 the form of organic compounds) in expressed yeast juice is 

 converted by this digestion into phosphoric acid, and that the 

 greater part of the phosphorus can be identified as present in this 



