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THERMAL DEATH-POINTS 75 
even a temperature of 55°-60° C. is fatal to Torule 
and Fungus spores (see pp. 62 and 65). 
(6) Death-point of Spores of Bacili after they have 
undergone Desiccation for a brief period 
This is a subject concerning which the most 
diverse statements have been made. Very great 
uncertainty exists even in regard to the ability to 
withstand desiccation possessed by the ordinary 
vegetative forms of Bacteria. One of the first to 
make observations on this latter subject was Burdon 
Sanderson,! who definitely came to the conclusion 
not only that ‘the germinal particles of microzymes 
are rendered inactive by thorough drying without 
the application of heat,” but also that “ fully-formed 
Bacteria are deprived of their power of further de- 
velopment by thorough desiccation.” The amount 
of desiccation adopted by Burdon Sanderson was 
merely that occasioned by keeping the organisms 
for two or three days in an uncovered condition 
exposed to a temperature of 104° F. Subsequent 
investigations, however, have shown that his con- 
clusion by no means holds good for all Bacteria, and 
that whether they survive or not depends much 
upon the conditions under which they undergo 
desiccation. His conclusion, also, most certainly 
does not apply to the spores of Bacilli, which were 
unknown at the time his observations were made. 
It remained, therefore, to ascertain by exact ex- 
periments what evidence could be obtained, in support 
1 Thirteenth Report of the Medical Officer of the Privy Council, 
1871, p. 61. 
