THEORY OF FERMENTATION 343 



passage of air, if such a thing were possible, between the 

 mercury and the sides of the delivery-tube was altogether 

 prevented, since the bacteria would consume every trace of 

 oxygen which might be dissolved in the liquid lying on the 

 surface of the mercury. Hence it is impossible to imagine 

 that the slightest trace of oxygen could have got into the 

 liquid in the flask. 



Before passing on we may remark that in this ready ab- 

 sorption of oxygen by bacteria we have a means of de- 

 priving fermentable liquids of every trace of that gas with a 

 facility and success equal or even greater than by the pre- 

 liminary method of boiling. Such a solution as we have 

 described, if kept at summer heat, without any previous 

 boiling, becomes turbid in the course of twenty-four hours 

 from a spontaneous development of bacteria; and it is easy 

 to prove that they absorb all the oxygen held in solution.* 

 If we completely fill a flask of a few litres capacity (about a 

 gallon) (Fie. 9) with the liquid described, taking care to 

 have the delivery-tube also filled, and its opening plunged 

 under mercury, and, forty-eight hours afterwards by means 

 of a chloride of calcium bath, expel from the liquid on the 

 surface of the mercury all the gas which it holds in solution, 

 this gas, when analyzed, will be found to be composed of a 

 mixture of nitrogen and carbonic acid gas, without the least 

 trace of oxygen. Here, then, we have an excellent means 

 of depriving the fermentable liquid of air; we simply have 

 completely to fill a flask with the liquid, and place it in the 

 oven, merely avoiding any addition of butyric vibrios, before 

 the lapse of two or three days. We may wait even longer; 

 and then, if the liquid does become impregnated sponta* 

 neously with vibrio germs, the liquid, which at first was 

 turbid from the presence of bacteria, will become bright 

 again, since the bacteria, when deprived of life, or, at least, 

 of the power of moving, after they have exhausted all the 

 oxygen in solution, will fall inert to the bottom of the vessel. 

 On several occasions we have determined this interesting 

 fact, which tends to prove that the butyric vibrios cannot be 

 regarded as another form of bacteria, inasmuch as, on the 



On the rapid absorption of oxygen by hactrria, *ee alto our 

 Of 1872, fur Its Generations ditet Spontantes, especially the note on page 78* 



