86 THE EVOLUTION OF LIFE 
life, and possibly, in consequence thereof, are capable 
of resisting degrees of heat far higher than those 
which prove fatal to ordinary bacteria, including 
Bacilli, Micrococci, Streptococci, and Staphylococci. 
These latter, as we have seen in their vegetative 
forms, are, like Torule and Fungus-germs, killed 
by a brief exposure to 140° F. (60° C.), or there- 
abouts ; while the more resistant, though much less 
widely distributed, spores of ordinary Bacilli have 
been shown to be killed, with only one exception, out 
of very numerous trials, when immersed in fluids that 
have been raised to the boiling point for 20’. 
After this exhaustive enquiry as to the degree of 
heat to which it is needful to expose our closed 
experimental vessels and their fluid contents, in 
order to feel reasonably sure that all pre-existing 
living things within them have been killed, we are 
in a position to take up the further enquiry, to which 
this has been a necessary preliminary, as to whether 
certain fluids, over and above their power of 
nourishing living things, are capable of actually 
engendering them. We have seen (p. 57) that some 
fluids are ‘“‘ nourishing” fluids only ; we now have to 
ascertain whether some of these same fluids under 
other conditions, or other fluids altogether, may not, 
in addition, be “generating” fluids for different 
kinds of Bacteria, for Torule, and for some simple 
Moulds. 

