352 LOUIS PASTEUR 



the movements are very active, in consequence of the con- 

 stant supply of air. In spite of the speedy death of the bac- 

 teria beneath the centre of the glass, we see life prolonged 

 there if by chance a bubble of air has been enclosed. All 

 round this bubble a vast number of bacteria collect in a thick, 

 moving circle, but as soon as all the oxygen of the bubble 

 has been absorbed they fall apparently lifeless, and are scat- 

 tered by the movement of the liquid. 9 



We may here be permitted to add, as a purely historical 

 matter, that it was these two observations just described, 

 made successively one day in 1861, on vibrios and bacteria, 

 that first suggested to us the idea of the possibility of life 

 without air, and caused us to think that the vibrios which we 

 met so frequently in our lactic fermentations must be the 

 true butyric ferment. 



We may pause to consider an interesting question in refer- 

 ence to the two characters under which vibrios appear in 

 butyric fermentations. What is the reason that some vibrios 

 exhibit refractive corpuscles, generally of a lenticular form, 

 such as we see in FIG. 14. We are strongly inclined to be- 

 lieve that these corpuscles have to do with a special mode 

 of reproduction in the vibrios, common alike to the anaero- 

 bian forms which we are studying, and the ordinary aerobian 

 forms in which also the corpuscles of which we are speaking 

 may occur. The explanation of the phenomenon, from our 

 point of view, would be that, after a certain number of fis- 

 siparous generations, and under the influence of variations in 

 the composition of the medium, which is constantly changing 

 through fermentation as well as through the active life of 

 the vibrios themselves, cysts, which are simply the refrac- 

 tive corpuscles, form along them at different points. From 

 these gemmules we have ultimately produced vibrios, ready 

 to reproduce others by the process of transverse division 

 for a certain time, to be themselves encysted, later on. 

 Various observations incline us to believe that, in their ordi- 



8 We find this fact, which we published as long ago as 1863, confirmed 

 in a work of H. Hoffman's, published in 1869 under the title of Memoir e 

 sur les bacteries, which has appeared in French (Annales des Sciences 

 naturelles, 5th series, vol. ix.). On this subject we may cite an observa- 

 tion that has not yet been published. Aerobian bacteria lose all power of 

 movement when suddenly plunged into carbonic acid gas; they recover it. 

 however, as if they had only been suffering from anaesthesia, as soon 9 

 they are brought into the air again. 





