ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 325 



Chemical Changes. 



Enzyme Action. — A. J. Brown* shows that the enzyme action 

 involved in the alcoholic fermentation of yeast follows approximately 

 the same order of progression as that of inversion of cane sugar. When 

 invertase acts in solutions of cane sugar of varying concentrations, an 

 approximately constant weight of sugar is inverted in unit time, and the 

 yeast-cell under similar conditions, ferments an approximately constant 

 weight of sugar. This apparent independence of mass-action may be due 

 to the existence of a time factor. If the enzyme, as there is reason to 

 believe, combines with the reacting substance, the compound molecule 

 may exist for an interval of time before disruption and change super- 

 vene. This will set a limit to the number of changes which a given 

 molecule of the enzyme can effect in unit time. Hence, provided that tho 

 quantity of reacting substance present ensures a greater number of 

 molecular collisions in unit time than the possible number of molecular 

 changes, then a constant weight of substance may be changed in unit 

 time in all the actions. The author brings forward experimental evi- 

 dence in support of this theory. 



Horace T. Brown and T. A. Glendinning f find the results of their 

 experiments on starch hydrolysis by diastase to agree with the observa- 

 tions of Adrian Brown and V. Henri on cane-sugar hydrolysis, and 

 suggest that one fundamental law may be found to express the rate of 

 change in all enzyme actions which can be quantitively studied with 

 sufficient accuracy. 



Tryptophane in Proteolysis. :£ — S. H. Vines describes further 

 experiments on the subject of proteolysis. These bear out his pre- 

 viously expressed opinion that the proteolytic enzymes of plants in 

 general are essentially " tryptic." The question arises, in view of the 

 accumulating evidence that pepsin itself can effect tryptic proteolysis, as 

 to whether such a thing as a peptic enzyme exists at all ; an enzyme, 

 that is, which only hydrolyses the higher proteids to peptones and does 

 not decompose the proteid molecule. The author suggests the following 

 provisional arrangement of plant enzymes from the point of view of the 

 reaction of the medium in which they act. 



I. Active in acid liquids. 



1. Active only in acid liquid. 



a. Most active with HC'l — Pepsin. 



b. Active with HC1 or natural acid — Nepenthin. 



2. More active in acid thau in neutral or alkaline liquid. 



a. Equally active with HC1 or natural acid — Bromelin, 



Coco. 



b. More active with natural or qrganic acid — Papain, 



Cradein, Peptase of barley. 

 II. Active in neutral or acid liquid — enzyme of yeast. 

 III. Active in neutral or alkaline liquid. 



a. Active in either — enzyme of Bean (?) ; putrefactive 



bacteria. 



b. More active in alkaline — Trypsin. 



" Joum. Cheni. So?., Ixxxi. (1902) pp. 373-88. t Tom. cit, pp. 388-400. 

 J Ann. Bot, xvi. (1902) pp. 1-22. Cf. this Journal, 1902, p. 205. 



