182 NEW BOOKS, AVITH SHORT NOTICES. [Sm;if^falTlT8S^ 
incontestably establish their spontaneous generation, M. Pouchet 
performed the following experiment, to whicL. we call attention : — 
' We plunged,' said he, ' a flask to the bottom of a vessel con- 
taining a decoction of malt which had been boiled for six hours ; 
there it was completely filled with this decoction, and it was 
carefully closed before it was brought to the surface. After- 
wards, with excessive precaution, the circumference of its mouth 
was luted with a compound of copal varnish and vermilion, and 
thus we were certain that the flask was hermetically sealed. At 
the end of six days — the external temperature having an average 
of 18° Centigrade — we saw a slight deposit of yeast at the bottom 
of the flask. The seventh day, the temperature of the laboratory 
being suddenly raised to 27° C., the flask burst with a loud report, 
and its upper half was blown to some inches' distance. Then we 
saw, with the naked eye, that a notable quantity of yeast had 
formed in the liquid under experiment, and the microscope demon- 
strated the fact beyond question.' ' If the spores had pre-existed 
in the liquid, it is admitted by all authorities that a moist 
temperature of 100° C, prolonged for six hours, would have com- 
pletely disorganized them. The yeast formed had, therefore, some 
other origin. It was not derived from the air, since the flask was 
completely removed from air. It was therefore spontaneously 
formed.' ' M. de Vaureal, who admits the importance of this expe- 
riment, and regards it as being a fundamental one, nevertheless 
complains of the very short time during which the flask was sus- 
pended in the liquid, and remarks, with some fairness, that it 
would have been more precise to have kept the flask in the liquid 
during the entire duration of ebullition. But M. Pouchet having 
in one of his experiments kept the flask in the liquid for ten 
minutes, M. Yaureal's objection loses its apparent force, and has 
merely a formal importance.' " 
The experiment detailed above by the author is one which, 
though of a simple character and easily tried by any one, is — the 
fact of the destruction of spores by heat being granted — a re- 
markably conclusive one, and it gets over one of the great objections 
of the panspermists. The doctrine of the latter, that the air is 
charged with the spores of fungi and the ova of Infusoria, is one more 
easily asserted than maintained. As we know from Dr. Hughes 
Bennett's experiments, the existence of atmospheric germs is 
extremely difficult to prove. On this point the author makes the 
following very pertinent remarks : — " If moreover the air, as the 
panspermists allege, is the vehicle of the germs of the plants which 
appear in fermentation, there would be no difficulty in discovering 
them ; their numbers would be considerable enough, and their size 
is most frequently very appreciable. M. Pasteur affirms, it is true 
— M. Pasteur always affirms — that we may distinguish the 
spores of the common moulds in the air ; but to affirm is not to 
demonstrate, and that which the eminent chemist fails to do, 
botanists are doing every day. Hoffmann recognizes clearly the 
spores of Cladosporium and Stemphylium ; M. Pouchet those of 
