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- 

 perature of which was maintained at 60 C. Four rabbits were now inocu- 

 lated by trephining 1 , 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 llth ; both died 

 with the characteristic symptoms of paralytic rabies on the third day. The 

 two rabbits inoculated with material exposed to 00 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 oil 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 inoculated 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 3 C., 

 and that 55 C. fails to destroy it, the time of exposure being ten minutes." 1 



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 

 pneumonise crouposse, 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 58 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- 



1 Report of the Committee on Disinfectants (op. cit.), p. 147. 



