Fig. 43 represents the rejuvenescence of this ferment. Comparing this figure with Fig. 42, we see that this ferment presents a considerable resemblance to “low” yeast in dimensions, method of budding, and oval shape; but the feature which distinguishes it essentially from “low” yeast is that it rises to the surface, like “high” yeast. Buoyed up by the gas during fermentation, it forms a layer of yeast on the surface of the fermenting liquid, where it remains after the head has fallen. Some of this head of yeast likewise adheres to the sides of the vessel above the level of the liquid. In short, by the greater regularity of its forms and the uniform dimensions of its cells, this ferment is to be easily distinguished from _saccharomyces pastorianus_; its aspect, which is oval instead of spherical, and the ramified form of its chains of cells, which is less marked than in the case of “high” yeast, also prevent our confounding it with the latter ferment; in its rising character it differs absolutely from “low” yeast; lastly, it may be distinguished from all other ferments by the flavour of the beer that it produces. The ferment which we discovered in this accidental way may be utilized. Indeed, we may ask, is it not to be found already in our beer? We are inclined to believe that it is. After the war of 1870, some Viennese traders established at Maisons-Alfort, near Paris, a manufactory of yeast for bakers. They saccharified by means of malt a mixture of the meals of rye, maize, and barley, which they then caused to ferment. One day we had occasion to study the yeast produced in this establishment, and although we did not submit it to a sufficient number of consecutive experiments to enable us to speak positively, we are under the impression that the yeast produced at Maisons-Alfort is a “high” one, differing from what may be properly termed the “high” yeast of breweries in which “high” fermentation is practised, but presenting a great resemblance to the “high” yeast of which we have been speaking. It would be interesting to confirm the opinion of their possible identity by fresh studies, and the best way of doing this would be to compare the qualities of beer which the two yeasts could produce. _Caseous Ferment._—We give the title caseous for a reason that will presently appear, to a ferment which we came across also accidentally. We were trying different methods of purifying yeasts, and for this purpose had composed a liquid formed of: Ordinary wort 150 c.c.[104] Water saturated with bi-tartrate of potash 50 c.c. Alcohol of 90° 25 c.c. Quantities of this liquid were placed in several of our double-necked flasks, submitted to boiling, then, after cooling, impregnated with different ferments, and kept in a water-bath at 50° C. (122° F.) for one hour.