182 STUDIES ON FERMENTATION. 



infusoria in general. All these foreign organisms would tend 

 to develop just in proportion as the conditions of the media 

 were more or less favourable to their growth, and, in a very 

 few days, our flasks would be filled with swarms of beings 

 which, in most cases, would entirely conceal the facts relating 

 to those forms, the separate study of which it was our object 

 to follow out. We shall have occasion, therefore, to examine, 

 in a subsequent paragraph, the preparation of ferments in a 

 state of purity. At present we may state that yeast, which 

 in its ordinary condition is a mass of cells so liable to 

 change that its preservation in a moist state is impossible, 

 manifesting in the course of a few days during the winter, 

 and in twenty-four hours during the heat of summer, all 

 the signs of incipient putrefaction, thereby losing its distinc- 

 tive characteristics, is nevertheless capable, when pure, of 

 enduring the highest atmospheric temperatures for whole 

 years without showing the least signs of putrid change or con- 

 tamination with any other microscopic organisms, and without 

 the Cells losing their power of reproduction. In the pre- 

 sence of facts like these, the theory of spontaneous generation 

 must seem chimerical. The hypothesis of the possible trans- 

 formation of yeast into penicilliiim g/nucum, bacteria, and 

 vibrios, or conversely, which the theories of Turpin, H. 

 Hoffmann, Berkeley, Trecul, Hallier, and Bechamp involve, 

 is equally refuted by these facts. 



^ II. — On " Spontaneous " Ferment. 



The expression spontaneous ferment may be applied to any 

 ferment that appears in a fermentable liquid without having 

 been purposely sown in it. In this respect the ferments men- 

 tioned in the preceding paragraph, those of all saccharine 

 juices of fruit which ferment when left to themselves — the 

 ferments of wine, for example — are spontaneous. The term, 

 however, is not altogether appropriate, because, after all, the 

 process is the same as if an actual sowing had been made, since, 



