We employed 60 cc. (about 2 fluid ounces) of yeast-water, sweetened with two percent. of sugar and impregnated with a trace of yeast. After having subjected our vessel to a temperature of 25 degrees C. (77 degrees F.) in an oven for fifteen hours, the drawn-out point was brought under an inverted jar filled with mercury and the point broken off. A portion of the gas escaped and was collected in the jar. For 25 cc. of this gas we found, after absorption by potash 20.6, and after absorption by pyrogallic acid, 17.3. Taking into account the volume which remained free in the flask, which held 315 cc., there was a total absorption of 14.5 cc. (0.83 cub. in.) of oxygen. [Footnote: It may be useful for the non-scientific reader to put it thus: that the 25 cc. which escaped, being a fair sample of the whole gas in the flask, and containing (1) 25-20.6=4.4 cc., absorbed by potash and therefore due to carbonic acid, and (2) 20.6-17.3=3.3 cc., absorbed by pyrogallate, and therefore due to oxygen, and the remaining 17.3 cc. being nitrogen, the whole gas in the flask, which has a capacity of 312 cc., will contain oxygen in the above portion and therefore its amount may be determined provided we know the total gas in the flask before opening. On the other hand we know that air normally contains approximately, 1-5 its volume of oxygen, the rest being nitrogen, so that, by ascertaining the diminution of the proportion in the flask, we can find how many cubic centimeters have been absorbed by the yeast. The author, however, has not given all the data necessary for accurate calculation.--D.C.R.] The weight of the yeast, in a state of dryness, was 0.035 gramme. It follows that in the production of 35 milligrammes (0.524 grain) of yeast there was an absorption of 14 or 15 cc. (about 7/8 cub. in.) of oxygen, even supposing that the yeast was formed entirely under the influence of that gas: this is equivalent to not less than 414 cc. for 1 gramme of yeast (or about 33 cubic inches for every 20 grains). [Footnote: This number is probably too small; it is scarcely possible that the increase of weight in the yeast, even under the exceptional conditions of the experiment described, was not to some extent at least due to oxidation apart from free oxygen, inasmuch as some of the cells were covered by others. The increased weight of the yeast is always due to the action of two distant modes of vital energy-- activity, namely, in presence and activity in absence of air. We might endeavor to shorten the duration of the experiment still further, in which case we would still more assimilate the life of the yeast to that of ordinary moulds.] Such is the large volume of oxygen necessary for the development of one gramme of yeast when the plant can assimilate this gas after the manner of an ordinary fungus.