254 Dr. A. Macfailym, I 'r. (1. II. M'.rris. anl Mr. S. 



volume which in many eases exceeded that given by the same amount 

 of juice to which sugar had been added. This auto-fermentation 

 apparently escaped the observation of Buchner, who only incidentally 

 refers to it in one of his papers, and who does not appear to have 

 made any correction for the gas evolved from the juice itself in any 

 of his experimental results. The extent to which this fermentation 

 occurs may be seen from the subsequent tables (Tables I and II) ; in 

 one experiment, for instance, 100 c.c. of the fresh juice gave no less 

 than 2'98 grammes or 1500 c.c. of carbon dioxide. This spontaneous 

 evolution of gas takes place even when the juice is kept at a tempera- 

 ture sufficiently low to maintain it in a solid condition. In all prob- 

 ability the gas which Buchner mentions as being evolved on heating 

 " Zymase " is due to this cause. 



In our earlier experiments we determined the carbon dioxide evolved 

 from the juice alone, or from its admixture with sugar, by measuring 

 the volume of saturated salt solution which was displaced by the gas ; 

 but later we adopted a modification of Hart's double titration method, 

 in which the carbon dioxide was absorbed by sodium hydroxide 

 solution, and the amount determined by double titration. 



In the experiments on the relationship of the carbon dioxide and 

 alcohol formed, we absorbed the carbon dioxide evolved in 33 per 

 cent, potassium hydroxide solution contained in Mohr's potash bulbs. 

 The alcohol formed in these experiments was estimated by distillation 

 and determination of the specific gravity of the distillate, the weight 

 of absolute alcohol corresponding to the gravity of the distillate being 

 then found by reference to spirit tables. 



Control experiments were made in all cases that is to say, when we 

 were determining the amount of carbon dioxide or of alcohol, formed 

 by any juice from sugar, a corresponding quantity of the juice was 

 placed under identical conditions, but without the addition of any 

 sugar, and the amount of gas evolved or of alcohol formed was care- 

 fully determined by the same methods as those used in the experiments 

 in the presence of sugar. We employed antiseptics to inhibit the 

 possible action of yeast-cells or other micro-organisms, the nature of 

 the antiseptics used depending on the object of the experiment. The 

 antiseptics principally employed were sodium arsenite, toluol, and 

 thymol, all at the rate of 1 per cent. 



In our earlier experiments we employed 40 per cent, of cane-sugar, 

 this being the concentration which Buchner first considered the most 

 favourable ; but we subsequently reduced this to 10 per cent., as we 

 found that greater action was obtained with the lesser concentration. 

 In fact, the larger amount of sugar appeared to exercise a retarding 

 influence on the activity of the juice. 



Xi'ture of Results obtained. In Table I we give the results of some of 

 our experiments, in which the gas evolved was measured by the dis- 



