342 LOUIS PASTEUR 



carbonic acid, we passed into it with all necessary precau- 

 tions 10 cc. (0.35 fl. oz) of a liquid similar to that described, 

 which had been already 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 prevent the access 

 of air. In this way the impregnation was accomplished with- 

 out 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 until April Qth 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 car- 

 bonate of lime in crystals. 



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

 mode of procedure adopted, everything combined to prevent 

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

 the beginning of the experiment, partly because of the in- 

 creased temperature in the oven and partly 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 medium we know for the growth of bacteria, 

 it speedily swarmed with these organisms.* In this way any 



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

 bacteria in 1872, described, after Mayer, the composition of a liguid pecu- 

 liarly adapted to the propagation of these organisms, which it would be well 

 to compare for its utility in studies of this kind with our solution of lactatc 

 and phosphates. The following is Cohn's formula: 



Distilled water 20 cc. (0.7 fl. oz.) 



Phosphate of potassium o.i gramme (1.5 grains) 



Sulphate of magnesium o.i 



Tribasic phosphate of lime o.oi (0.15 grain) 



Tartrate of ammonia 0.2 (3 grains) 



This liquid, the author says, has a feeble acid reaction and forms a 

 fectly clear solution. 



