the second place, the phenomena of chemical and organogenic synthesis, corresponding to the growth of the yeast and the multiplication of its protoplasm. The former are no longer detected, as we have just said, by striking manifestations. However, it is not true that everything which is visible and which may be isolated outside the activity of the yeast is part of those phenomena. The boiling of the juice or the mash, the heat given off by the copper, all this phenomenal apparatus is but the consequence of the production of the carbonic acid and of its liberations—_i.e._, the consequence of the act of destruction of the sugar. Here is organic destruction with its energetic manifestations! This example of the life of brewers’ yeast, of the saccharomyces, specially chosen by Le Dantec as being absolutely clear and giving the best illustration of his argument, contradicts him at every point. The general thesis of this vigorous thinker is that we cannot distinguish between the two parts of the vital act, organic destruction, and assimilating synthesis; that these two acts are not successive; that they give rise to phenomenal manifestations equally evident, apparent, or striking. Now, in the case of yeast, the phenomenon of destruction is clearly distinct from that of the assimilating synthesis which multiplies the substance of the saccharomyces. In fact, the action is realized by means of an alcoholic diastase manufactured by the cell; and Büchner succeeded in isolating this alcoholic ferment which splits up the sugar into alcohol and carbonic acid, and also _in vitro_ and _in vivo_, makes the vat boil and heats the liquid. All the yeast is at work at once, says M. Dantec. No, and this is the proof. And, further, Pasteur himself, who had shown the relation of the decomposition of the sugar to the fact of the growth of the yeast and of the production of accessory substances such as succinic acid and glycerine, always referred to _correlation_ between these phenomena. The destruction of the sugar is the _correlative_ of the life of the yeast. This was his favourite formula. It never entered his head that there could be a confusion instead of a correlation, and that there might be only one and the same act, the phases of which would be indistinguishable. This unfortunate idea, which was fated to be so rapidly contradicted, is due to Le Dantec. Far from it being the case, Pasteur had distinguished the _ferment function_ from the life of the yeast. According to him, the yeast may exist sometimes as a ferment and sometimes otherwise. § 3. CORRELATION OF TWO ORDERS OF VITAL FACTS.