196 STUDIES ON FEIIMENTATIOX. 



the weight of new yeast which, it yields is always less than 

 that yielded by " high " yeast, for the same quantity of 

 fermentable liquid, although greater than that which saccha- 

 romi/ces pasioriaiins would give. Lastly, the beer possesses 

 a flavour and delicacy which cause it to be held in higher 

 esteem bj consumers than beers produced by means of other 

 ferments.* 



§ IV. — On the Existence and Production of Other Species 



OF Ferment. 



Our present knowledge of the alcoholic ferments embraces the 

 following, without taking into account the ferment-form of 

 niucor : — 



The ferment named after the author, which is found associated, 

 with the ferments of the grape and other domestic fruits, and- 

 with spontaneous ferments in general. 



The ferment of " high " beer. 



The ferment of " low " beer. 



To these must be added the ordinary ferment of wine, and 

 that called (qjiculatiis, although, indeed, these last are of little 

 practical importance, since, in general, they soon become lost 

 amongst others of greater vitality, in the spontaneous fermenta- 

 tion of fruits. These are not the only alcoholic ferments ; a 

 study of the germ-cells diffused over the surface of fruits, 

 grains, and stalks of all vegetables in different countries, would 

 doubtless lead to the discovery of many new ones. We are even 

 inclined to believe that one ferment might give rise to a multi- 

 tude of others. The investigations which we have undertaken 

 in this direction are as yet not far advanced ; we may, however, 

 be allowed merely to state the principle which governs them. 

 A ferment is a combination of cells, the individuals of which 

 must differ more or less from each other. Each of these cells 



* [On this point again Dr. Graliam expresses some dissent (" Nature," 

 loc. cit.) : " Here surely M. Pasteur must be thinking rather of the inferior 

 products of the surface fermentation in France and Germany, than of 

 those of England and Scotland." — D. C. E.] 



