404 BACTERIA IN CROUPOUS PNEUMONIA. 



rather scanty, almost homogeneous, and semi-transparent. Upon 

 potato no development occurs, even in the incubating oven. Milk is 

 a favorable culture medium, and the casein is coagulated as a result 

 of its presence. 



It ceases to grow on solid media at about 40 C., and in favorable 

 liquid media at 42 C. Its thermal death-point, as determined by 

 the writer, is 52 C. , the time of exposure being ten minutes. It 

 loses its vitality in cultures in a comparatively short time four or 

 five days on agar and is very sensitive to the action of germicidal 

 agents. Its pathogenic power also undergoes attenuation very 

 quickly when it is cultivated in artificial media, but may be restored 

 by passing it through the bodies of susceptible animals. Attenua- 

 tion of virulence may also be effected by exposing bouillon cultures 

 to a temperature of 42 C. for twenty-four hours, or by five days' 

 exposure to a temperature of 41 C. 



Emmerich reported in 1891 to the Congress of Hygiene and 

 Demography in London the results of experiments made by him 

 relating to immunity in rabbits and mice. Rabbits were rendered 

 immune by the intravenous injection of a very much diluted but 

 virulent culture of the micrococcus. The flesh of these immune 

 rabbits was rubbed up into a fine paste, and the juices obtained by 

 compressing it in a clean, sterilized cloth. This bloody juice was kept 

 for twelve hours at a temperature of 10 C., and then sterilized by 

 passing it through a Pasteur filter. Some of this juice was injected 

 into a rabbit, which with twenty-five others was then made to re- 

 spire an atmosphere charged with a spray of a bouillon culture of 

 the micrococcus. As a result of this all of the rabbits died except the 

 one which had previously been injected with the immunizing juice. 

 In a similar experiment upon mice six of these animals, which had 

 previously been injected with the immunizing juice, survived the in- 

 jection of a full dose of a virulent culture, while a control mouse, 

 not previously injected with the juice, promptly died after receiving 

 the same quantity of the virulent culture. 



The writer in 1881, in experiments made to determine the value 

 of various disinfectants, as tested upon this micrococcus, obtained 

 experimental evidence that its virulence is attenuated by the action 

 of certain antiseptic agents. Commenting upon the results of these 

 experiments in my chapter on " Attenuation of Virus," in " Bacte- 

 ria " (1884), I say : 



' ' Sodium hyposulphite and alcohol were the chemical reagents which 

 produced the result noted in these experiments ; but it seems probable that 

 a variety of antiseptic substances will be found to be equally effective when 

 used in the proper proportion. Subsequent experiments have shown that 

 neither of these agents is capable of destroying the vitality of this septic 

 micrococcus in the proportion used (one per cent of sodium hyposulphite or 



