258 PASTEUR, ON FERMENTS. 



number of flasks in which it coagulates from the presence of 

 Infusoria diminishes progressively in proportion to the 

 longer duration of the ebullition. And lastly, if the ebulli- 

 tion be carried on at a temperature of 110 to 112 degrees, 

 under the pressure of H atmosphere, the milk will never 

 afford any Infusoria. Consequently, as they do arise under 

 the conditions existing in the former experiments, this is 

 evidently due to the circumstance that the fecundity of the 

 germs of the Vibrios is not entirely destroyed, even in water 

 at a temperature of 100°, kept up for some minutes, and 

 that it is more affected by a longer ebullition at that tem- 

 perature, and wholly abolished at the temperature of 110° to 

 112° C. 



But what is to be said concerning the phenomenon of the 

 coagulation under those special conditions of ebullition, in 

 which the milk in contact with calcined air never affords 

 any Infusoria? One remarkable fact is, that the milk does 

 not coagulate. It remains alkaline, and preserves, I would 

 venture to say, entirely all the properties of fresh milk. 

 Then if, into this milk, thus retaining its integrity, the 

 atmospheric dusty particles are introduced, it changes and 

 coagulates, and the microscope shows the existence in it of 

 divers animal and vegetable productions. 



It would be very interesting to ascertain whether the 

 fluids belonging to the animal economy, such as milk and 

 urine, contain normally or accidentally, previously to all 

 contact with the common air, the germs of organized pro- 

 ductions. This is a question which I hope to resolve in a 

 subsequent communication. 



The generally admitted theory of ferments, and that which 

 of late years had received fresh support from the writings 

 or the labours of various chemists, consequently appears 

 to me more and more incongruous with experiment. The 

 "ferment" is not a dead substance, without determinate 

 specific properties. It is a being, whose germ is derived 

 from the air. It is not an albuminous substance, altered by 

 oxygen. The presence of albuminous matters is an indis- 

 pensable condition of all fermentation, because the " ferment" 

 depends upon them for its life. They are indispensable 

 in the light of an aliment to the ferment. The contact 

 of the atmospheric air is, primarily, equally an indispensable 

 condition of fermentation, but it is so in virtue of its being 

 a vehicle of the germs of the " ferments." 



What is the true nature of these germs? Do they not 

 require oxygen, in order to pass from the state of genus to 

 that of adult ferments, such as are met with in the products 



