358 LOUIS PASTEUR 



air? Now, what bearing can the question of the animal 

 or vegetable nature of the ferment, of the organized being, 

 have upon the investigation of these two problems? In 

 studying butyric fermentation, for example, we endeavoured 

 to establish these two fundamental points; i. The butyric 

 ferment is a vibrio. 2. This vibrio may dispense with air 

 in its life, and, as a matter of fact, does dispense with it in 

 the act of producing butyric fermentation. We did not 

 consider it at all necessary to pronounce any opinion as to 

 the animal or vegetable nature of this organism, and, even 

 up to the present moment, the idea that vibrio is an animal 

 and not a plant is in our minds, a matter of sentiment 

 rather than of conviction. 



M. Robin, however, would *iave no difficulty in determin- 

 ing the limits of the two kingdoms. According to him, 

 " every variety of cellulose is. we may say, insoluble in 

 ammonia, as also are the reproductive elements of plants, 

 whether male or female. Whatever phase of evolution the 

 elements which reproduce a new individual may have 

 reached, treatment with this reagent, either cold or raised 

 to boiling, leaves them absolutely intact under the eyes 

 of the observer, except that their contents, from being 

 partially dissolved, become more transparent. Every vege- 

 table whether microscopic or not, every mycelium and every 

 spore, thus preserves in its entirety its special characteristics 

 of form, volume and structural arrangements; whilst in the 

 case of microscopic animals, or the ova and microscopic 

 embryos of different members of the animal kingdom, the 

 very opposite is the case/' 



We should be glad to learn that the employment of a 

 drop of ammonia would enable us to pronounce an opinion 

 with this degree of confidence on the nature of the lowest 

 microscopic beings; but is M. Robin absolutely correct in 

 his assumptions? That gentleman himself remarks that 

 spermatozoa, which belong to animal organisms, are in- 

 soluble in ammonia, the effect of which is merely to make 

 them paler. If a difference of action in certain reagents, 

 in ammonia, for example, were sufficient to determine the 

 limits of the animal and vegetable kingdoms, might we not 

 argue that there must be a very great and natural difference 





