374 THE BEGINNINGS OF LIFE. 



occurrence of fermentation, so that they often found 

 no organisms when their flasks were opened. But on 

 subjecting other experimental fluids to the same tem- 

 perature, though exposing them subsequently to quite 

 different conditions supposed by myself to be more 

 favourable for the occurrence of fermentative changes 

 I do find organisms in the fluids when the flasks are 

 opened. 



It must then never be lost sight of that the negative 

 results of Schwann, M. Pasteur, and others, may be only 

 applicable to the particular fluids and the particular 

 conditions under which they worked; but the multi- 

 tudes of positive results legitimately obtained by myself 

 and other experimenters, must have a most important 

 bearing upon the settlement of the general doctrine. 



As previously stated, M. Pasteur himself for a long 

 time obtained only negative results in repeating the 

 experiments of Schwann. In his earlier investigations 

 he had generally made use of c Peau de levure sucree/ 

 of urine, or of some other fluid which was naturally 

 unfitted to undergo fermentative changes of marked 

 intensity, or even to nourish the higher infusorial organ- 

 isms 1 . But there came a time when M. Pasteur chanced 



1 Whether the organisms found in a given fluid have been actually 

 produced therein, or have only undergone development in it, we may, 

 for the sake of argument, measure the evolutional capacity of a fluid by 

 the amount and kinds of organisms which are produced in a given 

 quantity of it, in a definite time, and at a given temperature. We cer- 

 tainly must not judge of the evolutional qualities of a fluid by its mere 

 tendency to emit a bad odour in a short space of time. A certain fluid 



