158 INFLUENCE OF PHYSICAL AGENTS. 
ments the spores of Bacillus anthracis and of Bacillus alvei failed to 
grow after exposure to a temperature of 100° C. for four minutes, 
and only a few colonies developed after two minutes’ exposure to this 
temperature. The thermal death-point of spores of the “‘ wurtzel ba- 
cillus” and of Bacillus butyricus (of Hueppe) was the same—100° C. 
for four minutes. 
Schill and Fischer, in 1884, made a number of experiments to de- 
termine the thermal death-point of Bacillus tuberculosis. They 
found that five minutes’ exposure to a temperature of 100° C. in 
steam destroyed the vitality of the bacillus in sputum in five min- 
utes. When the time was reduced to two minutes a negative result 
from inoculation was obtained in two guinea-pigs, but one inoculated 
at the same time became tuberculous. My own experiments and 
those of Yersin, made since, lead me to think that there may have 
been some cause of error in this experiment of Schill and Fischer, 
and that the thermal death-point of the spores of Bacillus tuber- 
culosis is considerably below the boiling point of water. I inoculated 
guinea-pigs with tuberculous sputum subjected for ten minutes to 
the following temperatures: 50°, 60°, 70°, 80°, 90° C. The animal 
inoculated with material exposed to 50° died from tuberculosis at the 
end of seven weeks. None of the others developed tuberculosis. 
Yersin exposed an old culture in glycerin bouillon, in which many 
of the bacilli contained spores—‘‘ trés nettes”—to the following tem- 
peratures : 55°, 60°, 65°, 70°, '75°, 80°, 85°, 90°, 100° C. ‘* At theend of 
ten days the bacilli heated to 55° gave a culture in glycerin bouillon ; 
those exposed to 60° grew after twenty-two days; none of the 
bacilli heated above 70° gave any development. This experiment, 
repeated a great number of times, has always given us the same re- 
sult.” Voelsh, who has studied the same question, reports as the 
result of his experiments that the tubercle bacillus in sputum was 
not destroyed by heating to 100° C. Further experiments will be re- 
quired to reconcile these contradictory results. 
While the spores of the pathogenic bacteria mentioned are de- 
stroyed by the boiling point of water within a few minutes, certain 
non-pathogenic species resist this temperature for hours. Thus 
Globig obtained a bacillus from the soil the spores of which required 
five and one-half to six hours’ exposure to streaming steam for their 
destruction. These spores survived exposure for three-quarters of an 
hour in steam under pressure at from 109° to 113° C. They were de- 
stroyed, however, by exposure for twenty-five minutes in steam at 
113° to 116°, and in two minutes at 127°. 
In the practical application of steam for disinfecting purposes it 
must be remembered that, while steam under pressure is more effec- 
tive than streaming steam, it is scarcely necessary to give it the pre- 
