PASTEUR ON FERMENTATION. 711 



remain absent forever, because that whicli constitutes essentially the 

 life of those beings, for the nourishment of which this liquid is appro- 

 priate, has not been added. Let us then introduce life there, let us 

 sow vibrios in it. We place in the little funnel which surmounts the 

 straight tube of our flask, the one closed by a glass faucet, a small quan- 

 tity of one of those organic liquids in which vibrios are found after ex- 

 posure to the air ; or, better yet, and that is what has been done here, 

 let us place in the funnel some liquid, the same exactly as that con- 

 tained in the flask, but which has been exposed to the air and in 

 which vibrios have appeared. Let us now turn the faucet and intro- 

 duce a few drops with their vibrios into the flask. 



Singular phenomena appear soon after this sowing of life in our 

 mineral solution. The liquid, which was as limpid as distilled water, 

 becomes little by little opalescent during the following days, and at 

 the same time gases are set free and rise in the form of small bubbles 

 to the top of the flask. This gas is a mixture of hydrogen and car- 

 bonic acid, and at the same time tlie lactic acid is translbrmed into 

 butyric acid, which unites with a part of the lime of the lactate, the 

 rest of which combines with the carbonic acid. It is a real putrefac- 

 tion of the lactic acid which has taken place, but a putrefaction 

 without putridity, for the lactic acid contains neither sulphur nor 

 phosphorus, those elements of ofiensive gaseous combinations which 

 are deleterious for man but inofiensive for vibrios. No, I am wrong : 

 putridity shows itself, but in so slight a degree that it is almost inap- 

 preciable. Phosphorus and sulphur are present in the phosphates and 

 sulphates ; these are decomposed, hence a slight odor and even quite 

 frequently a gray color given to the precipitate, probably by a little 

 sulphuret of iron, for iron is almost always present, even in the purest 

 materials. 



Whence come all these mysterious transformations ? Microscopi- 

 cal examination of a drop of this liquid which has lost its primitive 

 limpidity will tell us. Wonderful spectacle ! Beings in the form of 

 small rods go and come, stop and recommence their movements. 

 They are single or united in pairs, twos, threes, and even more. Here 

 are a pair which separate from one another by a sort of effort, more 

 or less prolonged on the part of the two individuals composing it. 

 And now each half has its own movements; this is generation by 

 scission. Now 1 know why the liquid is milky. What our eyes in 

 their weakness call milkiness the microscope shows us is a conse- 

 quence of tlie life of these little beings and of their incessant move- 

 ments. And the experiment, patiently followed out, will tell us that 

 the life lasts as long as does the principal food of our little beings, that 

 is, the lactic acid of the lactate of lime, provided always that all the 

 other general conditions of existence be satisfied ; for it is not enough 

 to have food at our disposal, we must be able to assimilate it, and it is 

 necessary that the functional trouble which yoii call pathology should 



