134 
M. A. CHAUVEAU. 
of culture, taken from the oven at -f- 47° in another, heated only 
to -(- 32°-35°. The evolution then begins again its normal course; 
the proliferation continues, and the development terminates by 
the formation of a great number of true spores. By the general 
aspect of the microscopic characters, these cultures do not differ 
sensibly from those which have not been submitted to these special 
conditions, unless the exposure to heat has been too lohg contin¬ 
ued. In general, four hours of heating at -f- 47° does not prevent 
the following evolution, or scarcely disturb it. 
The attenuating influence of heating of the cultures is not only 
temporary; it can be transmitted to a certain extent, when these 
cultures resume their course of evolution, to the spores born 
from the protoplasm of the threads and batonnets, which have re¬ 
ceived the action of heat. 
But where the transmission of this effect of heat is specially 
manifest, is in the facility with which these spores are brought 
under the weakening influence of a heating process applied di¬ 
rectly upon them. Nothing is easier or more simple than to 
render them almost absolutely harmless, by exposing them for 
some time to the action of a given temperature. I call attention 
to this new fact, which possesses special interest. It is not impos¬ 
sible to obtain a similar effect with the spores of normal origin, 
though rightly they are considered as susceptible of a strong re¬ 
sistance to causes of destruction, particularly to the influences of 
comparatively high temperatures. But these spores may be left, 
with impunity, for one hour or one hour and a half, exposed to 
a temperature of -f- 80°. They do not then undergo any sensible 
alterations in their morphological character, nor in their physio¬ 
logical properties. It is not so any more with spores of culture 
whose growth has been temporarily interrupted by heat. In this 
condition, this affects the objective character of the spore, which 
seems to become smaller, but is also greatly modified in its vir¬ 
ulent activity. The culture can then be inoculated, without great 
risk to life, to guinea-pigs, and especially to sheep, which thus ob¬ 
tain immunity, as well as with any other preventive inoculation. 
The culture of the second generation may, as well as this first 
means, prove the persistency of the vital activity of threads and 
