INFLUENCE OF PHYSICAL AGENTS. 157 
sterilized water. The milky emulsion was introduced into four capillary 
tubes, such as had been used in my experiments heretofore recorded. Two 
of these tubes were then placed for ten minutes in a water bath, the tem- 
erature of which was maintained at 60°C. Four rabbits were now inocu- 
ated by trephining, two with the material exposed to 60° C. for ten min- 
utes, and two with the same material from the capillary tube not so exposed. 
The result was as definite and satisfactory as possible. The two control 
rabbits were taken sick, one on March 10th and one on the 11th ; both died 
with the characteristic symptoms of paralytic rabies on the third day. The 
two rabbits inoculated with material exposed to 60° C. remained in perfect 
health. On the 26th of March one of these rabbits was again inoculated, 
by trephining, with material from the medulla of a rabbit just dead from 
hydrophobia. This rabbit died from paralytic rabies on the 8th of April. 
Its companion remains in perfect health. 
‘*A second experiment was made in the same way on the 14th of March. 
Two rabbits were inoculatéd with material exposed for ten minutes to a 
temperature of 50° C.; two with material exposed to 55° C.; and two con- 
trol rabbits with material not so exposed. One of the rabbits inoculated 
with material exposed to 50° C., and one of the control rabbits, died on the 
25th; the other rabbit inoculated with the material exposed to 50°, the other 
control, and one inoculated with material exposed to 55°, on the 26th. The 
second rabbit inoculated with material exposed to 55° died five days later 
with the characteristic symptoms of the disease. These experiments show, 
then, that the virus of hydrophobia is destroyed by a temperature of 60° C., 
and that 55° C. fails to destroy it, the time of exposure being ten minutes.”? 
The experimental data given show that the pathogenic bacteria 
tested and different kinds of virus are all killed by a temperature of 
60° C. or below; some, like the cholera spirillum and Micrococcus 
pneumonie croupose, failing to grow after exposure to as low a tem- 
perature as 52° C. for four minutes. By extending the time a still 
lower temperature will effect the same result. Thus, according to 
Chauveau, the anthrax bacillus is killed by twenty minutes’ exposure 
to a temperature of 50° C.; and Brieger sterilizes cultures of the 
diphtheria bacillus, to obtain the soluble toxalbumin produced in 
them, by exposure for several hours to 50° C. A temperature of 60° 
has been found to decompose the toxalbumin. The non-pathogenic 
bacteria tested have, as a rule, a higher thermal death-point—s8° C. 
for Bacillus prodigiosus, 64° C. for Sarcina lutea, etc. 
It is a remarkable fact that certain bacteria not only are not de- 
stroyed at higher temperatures than this, but are able to multiply at 
a temperature of 65° to 70°C. Thus Miquel, in 1881, found in the 
waters of the Seine a motionless bacillus which grew luxuriantly in 
bouillon at a temperature of 69° to 70°C. Van Tieghem has also 
cultivated several different species at about the same temperature, 
and more recently Globig has obtained from the soil several species 
which grow at temperatures ranging from 50° to 70° C. 
The resisting power of spores to heat also varies in different spe- 
cies ; but the spores of known pathogenic bacteria are quickly de- 
stroyed by a temperature of 100° C. (212° F.). In the writer’s experi- 
‘Report of the Committee on Disinfectants (op. cit.), p. 147. 
