Let us now return to the first experiment described in this paragraph (page 238), in which a flask of three litres capacity was filled with fermentable liquid, which, when caused to ferment, yielded 2·25 grammes of yeast, under circumstances where it could not obtain a greater supply of free oxygen than 16·5 c.c. (about one cubic inch). According to what we have just stated, if this 2·25 grammes (34 grains) of yeast had not been able to live without oxygen, in other words, if the original cells had been unable to multiply otherwise than by absorbing free oxygen, the amount of that gas required could not have been less than 2·25 × 414 c.c., that is, 931·5 c.c. (56·85 cubic inches). The greater part of the 2·25 grammes, therefore, had evidently been produced as the growth of an anaërobian plant. Ordinary fungi likewise require large quantities of oxygen for their development, as we may easily prove by cultivating any mould in a closed vessel full of air, and then taking the weight of plant formed and measuring the volume of oxygen absorbed. To do this, we take a flask of the shape shown in Fig. 66, capable of holding about 300 c.c. (10-½ fluid ounces), and containing a liquid adapted to the life of moulds. We boil this liquid and seal the drawn-out point, after the steam has expelled the air wholly or in part; we then open the flask in a garden or in a room. Should a fungus-spore enter the flask, as will invariably be the case in a certain number of flasks out of several used in the experiment, except under special circumstances, it will develop there and gradually absorb all the oxygen contained in the air of the flask. Measuring the volume of this air, and weighing, after drying, the amount of plant formed, we find that for a certain quantity of oxygen absorbed we have a certain weight of mycelium, or of mycelium together with its organs of fructification. In an experiment of this kind, in which the plant was weighed a year after its development, we found for 0·008 gramme (0·123 grain) of _mycelium_, dried at 100° C. (212° F.), an absorption that amounted to not less than 43 c.c. (1·5 cubic inches) of oxygen, at 25°. These numbers, however, must vary sensibly with the nature of the mould employed, and also with the greater or less activity of its development, because the phenomenon is complicated by the presence of accessory oxidations, such as we find in the case of _mycoderma vini_ and _aceti_, to which cause the large absorption of oxygen in our last experiment may doubtless be attributed.[120] [Illustration: Fig. 66.]