132 
M. A. CHAHVEAU. 
threads or short batonnets, analogous to the bacilli of the fresh 
blood upon which heat has such an effective action. 
The second step, corresponding to the stage of attenuation, 
does not require any delicate manipulation, any more, in fact, 
than the first. Removed from the thermostat at -f- 13°, the ma¬ 
trasses are placed in the second warming apparatus, after taking 
a'small pipette of the liquid, to test the activity of the cultures. 
Two factors act in the attenuation which heat gives to those 
cultures: the degree of elevation and the length of time of the 
exposure to that high temperature. If the strength of the first 
of ihese factors diminishes, that of the second must increase, 
and vice versa. From numerous experiments it results that a 
heating of three hours at a temperature of -f- 47° is sufficient to 
transform into agents harmlesss to the guinea-pig, the fluids and 
batonnets of cultures primitively very virulent. 
Heating does not modifiy the external aspect of the cultures. 
Indeed, it prevents in them, all proliferations of threads and 
batonnets, although it does not prevent development of the rudi¬ 
mentary spores. On the contrary, heating stimulates their 
multiplication or causes them to appear when they did not pre¬ 
viously exist. 
I have said, that with this method, the attenuation of the 
cultures can be graduated at will, in giving to the heating a 
duration in relation to the degree of attenuation it is desired to 
obtain. This is one of the interesting points of my research¬ 
es. To reach a greater certainty and give to the results of 
my experiments in inoculations every reliability, I always 
inoculated guinea-pigs by injecting under the skin of the thigh 
one or two drops of the liquid, according to the size of the 
animal. In those conditions, if one tries comparatively the 
same liquid of culture, supposed to be very active, before and 
after the heating, during one, two, three, or four hours, this is 
what he observes: all the animals inoculated with non-heated 
liquid die rapidly, that is, in about forty-eight hours, with a large 
asdema. Those which have received the liquid heated for one hour, 
die also, almost all, but death takes place generally later that in 
the first. The liquid heated two hours is much less active, as, 
