This extract closely resembles in properties the juice obtained by grinding the same yeast, but it is usually more active and contains more inorganic phosphate (see p. 46). /2. Other Methods./ Attempts to prepare active extracts from undried yeast in an analogous manner have so far not been very successful. Thus Rinckleben [1911] found that plasmolysis by glycerol (8 per cent.) or sodium phosphate (5 per cent.) sometimes yielded an active juice and sometimes a juice which contained enzyme but no co-enzyme, but more often an inactive juice incapable of activation (p. 64) [see also Kayser, 1911]. Giglioli [1911] by the addition of chloroform also obtained an active liquid. It appears in fact as though almost any method of plasmolysing the yeast cell may yield a certain proportion of zymase in the exudate. An ingenious process has been devised by Dixon and Atkins [1913] who applied the method of freezing in liquid air which they had found efficacious for obtaining the sap from various plant organs. They thus succeeded in obtaining from yeast, derived from Guinness' brewery in Dublin, liquids capable of fermenting sugar and of about the same efficacy as the maceration extracts prepared by Lebedeff's method from the same yeast. The results were, however, in both cases very low, the maximum total production of CO{2} by 25 c.c. of liquid from excess of sugar being 32·5 c.c. (air temperature) or about 0·06g. Munich yeast on the other hand yields, either by maceration or grinding, a liquid giving as much as 1·5-2g. of CO{2} per 25 c.c., whilst [p027] English yeast-juice prepared by grinding often gives as much as 0·5-0·7g. of CO{2}. No direct comparison with the juice prepared by grinding was made by Dixon and Atkins, but it may be concluded from their results that the best method of obtaining an active preparation from the top yeasts used in this country is that of grinding. Maceration, freezing and plasmolysis alike yield poor results. With Munich yeast on the other hand the maceration process yields excellent results, whilst the liquid air process has not so far been tried. PRACTICAL METHODS FOR THE ESTIMATION OF THE FERMENTING POWER OF YEAST-JUICE.