AND THE CAUSES OF FERMENTATION. 125 
Bacteria ; and, again, when the Toru/e begin to decay 
they are apt to incite a more or less manifest putre- 
faction, during. which the fluid gradually becomes 
turbid with Bacteria. It is, in fact, a general rule 
that putrefaction is apt to supervene upon a fermenta- 
tion of a more smouldering type. 
III. In the third subclass I include fluids which, 
after exposure to 212°F. or higher temperatures, are 
unable, either alone or under the influence of ordinary 
atmospheric particles or fragments, to undergo putre- 
faction, although such a process can invariably be 
initiated by bringing the fluids into contact with 
living ferments. As example of such fluids, I may 
‘cite the neutral saline solution to which I have so 
often referred and that known as Pasteur’s solution. 
Other fluids of the same kind have lately been re- 
ferred to by Professor Huizinga.** The fact that 
certain fluids cannot be made to undergo putrefac- 
tion by the influence of dead organic particles, al- 
though they become at once amenable to the influence 
of living units, unmistakably shows the superior 
potency of living ferments; their action has, more- 
over, invariably proved to be certain and inevitable in 
all the cases in which they were known to be present. 
Even these least fermentable fluids of our third sub- 
class invariably become turbid within three days after 
* See Nature, March 20, 1873, p. 380. 
