Microbic Diseases Indicidualbj Considered. 225 



1,000, ill ton minutes ; absolute alcohol in five minutes; 

 but contact with these agents must be much more pro- 

 longed in the case of tuberculous substances, sputa, 

 etc. Hence, for the destruction of the virulence of 

 these substances, moist heat should be preferred. 



The tubercle bacillus resists the action of the gastric 

 juice. 



Cultures. — Vegetation of the bacillus on artificial 

 media is not easily obtained ; the operation, however, 

 is only delicate for the first generation. The culture 

 media most favorable for this bacillus are those which 

 contain an addition of peptone, glycerin, and even of 

 glucose, in proper proportions. The incubating oven 

 should be kept at a temperature in the neighborhood 

 of 39°, that temperature being best suited for the 

 growth of the bacillus ; multiplication is impeded by 

 slight deviation from this temperature, and ceases 

 altogether at about 35°. As the germ is aerobic, the 

 culture medium should also be freely exposed to the 

 air. The sowing should be taken from virulent 

 products from young tuberculous animals in which 

 the evolution is rapid, and should be implanted at 

 once upon serum ; it is transferred several times upon 

 this medium before trusting it to others. 



On serum, at the end of twelve to fifteen days, 

 small, round, whitish grains appear, and slowly in- 

 crease in size ; these grains are slightly raised, dry, 

 and scaly in appearance ; their growth is very limited 

 in the first cultures and they become confluent only 

 after the fourth or fifth generation ; vegetation is then 

 more rapid and the whole surface of the serum be- 

 comes covered with a thin, dry film, studded with ver- 

 rucose prominences. 



