ACTION OF CARBOLIC ACID ON YEAST. 



273 



cent, solution of pure carbolic acid was added to it. 

 No change took place for the first few minutes, but 

 after a little time, a white cloudiness was formed 

 which gradually collected together into a coagulum. 

 On separating this and exposing it freely to the air, 

 it entirely resisted putrefactive decomposition. The 

 solution strained from the coagulum still contained 

 carbolic acid and uncoagulated albumen." 



In an exactly similar experiment, in which cresylic 

 acid was substituted for carbolic acid, the mixed solu- 

 tions remained clear for half-an-hour, showing that 

 this body has a still slighter affinity for albumen, and 

 rendering it evident that the tar acids do not owe 

 their special action to their coagulating properties on 

 albumen. 



The exertion by carbolic acid of a special action on 

 germination and upon the living matter of fungi, Mr. 

 Crookes thinks is proved conclusively by the fact that 

 it not only arrests fermentation instantly when in pro- 

 gress, but prevents all future fermentation, as shown in 

 the subjoined instances. " A few drops of carbolic acid 

 added to half a pint of sugar syrup and yeast in full 

 action immediately put a stop to the fermentation." 

 " Fresh brewer's yeast was first washed with a solu- 

 tion of one per cent, of carbolic acid and then with 

 water. Its power of inducing fermentation in a solu- 

 tion of sugar was entirely destroyed, although no per- 

 ceptible change in the appearance of the yeast cells 

 under the microscope could be detected. Repeated 



