294 STUDIES ON FEKMENTATION. 



vessel full of mercury and placed the whole apparatus in an 

 oven at a temperature varying between 25° C. and 30° C. 

 (77° F. and 86° F.) ; then, after having refilled the small 

 cylindrical tap-funnel with carbonic acid, we passed into it 

 with all necessary precautions 10 c.c. (0"35 fi. oz.) of a liquid 

 similar to that described, which had been ali'eady in active 

 fermentation for several days out of contact with air and now 

 swarmed with vibrios. We then turned the tap of the funnel, 

 until only a small quantity of liquid was left, just enough to pre- 

 vent the access of air. In this way the impregnation was accom- 

 plished without either the ferment-liquid or the ferment-germs 

 having been brought in contact, even for the shortest space, 

 with the external air. The fermentation, the occurrence of 

 which at an earlier or later period depends for the most part 

 on the condition of the impregnating germs, and the number 

 introduced in the act, in this case began to manifest itself by 

 the appearance of minute bubbles from March 29th. But not 

 till April 9th did we observe bubbles of larger size rise to the 

 surface. From that date onward they continued to come in 

 increasing number, from certain points at the bottom of the 

 flask, where a deposit of earthy phosphates existed ; and at 

 the same time the liquid, which for the first few days remained 

 perfectly clear, began to grow turbid in consequence of the 

 development of vibrios. It was on the same day that we first 

 observed a deposit on the sides of carbonate of lime in crj'stals. 

 It is a matter of some interest to notice here that, in the 

 mode of procedure adopted, everj^thing combined to prevent 

 the interference of air. A portion of the liquid expelled at the 

 beginning of the experiment, partly because of the increased 

 temperature in the oven and partl}^ also by the force of the gas, 

 as it began to be evolved from the fermentative action, reached 

 the surface of the mercury, where, being the most suitable me- 

 dium we know for the growth of bacteria, it speedily swarmed 

 with these organisms.* In this way any passage of air, if such 



* The naturalist Cohn, of Breslau, who published an excellent work 

 on bacteria in 1872, described, after Mayer, the composition of a liquid 



