Considering the small proportional rise in rate and the long period of accelerated fermentation, the agreement between the volume observed, 29·8 c.c., and that calculated from the phosphate, 32·2, is quite satisfactory [Harden and Young, 1910, 1.] Precisely the same relations hold for maceration extract, but in this case it must be remembered that a large amount of free phosphate is present in the extract, as much as 0·3129 grm. Mg{2}P{2}O{7} being obtained from 20 c.c. in one preparation, so that the original extract had the concentration of a 0·14 molar solution of sodium phosphate. It is in fact not improbable that the delay in the onset of fermentation sometimes observed with maceration extract (see Lebedeff, 1912, 2; Neuberg and Rosenthal, 1913) may be due to the presence of phosphate in so great an excess of the amount which can be rapidly esterified by the enzymes that the rate of fermentation is at first greatly lowered (see p. 71). When this phosphate is removed by incubation with glucose or fructose, the subsequent addition of phosphate produces the characteristic action and the extra carbon dioxide evolved is, as with other yeast preparations, equivalent to the phosphate added. An actual estimation carried out in this way gave 35 c.c. of CO{2} for an addition of phosphate equivalent to 32·9 c.c. [Harden and Young, 1912]. [p047] Within the limits imposed by the experimental conditions, then, the fact is well established that the addition of a soluble phosphate to a fermenting mixture of a hexose with yeast-juice, maceration extract, dried yeast, or zymin causes the production of an equivalent amount of carbon dioxide and alcohol. This fact indicates that a definite chemical reaction occurs in which sugar and phosphate are concerned, and this conclusion is confirmed when the fate of the added phosphate is investigated. If an experiment, such as one of those described above, be interrupted as soon as the rate of fermentation has again become normal, and the liquid be boiled and filtered, it is found that nearly the whole of the phosphorus present passes into the filtrate, but that only a small proportion of this exists as mineral phosphate, whilst the remainder, including that added in the form of a soluble phosphate, is no longer precipitable by magnesium citrate mixture [Harden and Young, 1905, 2]. A similar observation was made at a later date by Iwanoff [1907], who had previously observed [1905] that living yeast, like many other vegetable organisms, converted mineral phosphates into organic derivatives. Iwanoff employed zymin and hefanol (p. 38) instead of yeast-juice, and found that phosphates were thereby rendered non-precipitable by uranium acetate solution, but did not observe the accelerated fermentation caused by their addition.