200 



This enables the pathologist to distinguish it amid myriads 

 of other germs. The bacillus tuberculosis is a plant para- 

 site that lives in the animal body, but it may be cultivated 

 on artificial culture media, such as: agar agar or bouillon 

 containing 5 per cent, of glycerine, and blood serum. It 

 develops best at 100 to 102 degrees Fah. This germ may 

 also live and retain its vitality outside of the animal body 

 for an indefinite time ; its length of life out of the body will 

 depend upon heat, light, moisture and the material in which 

 it exists. Koch and other observers have found that in 

 many instances the tubercle bacillus has retained its vitality 

 for nine or ten months in the sputa or expectorations of 

 tuberculous persons. However, it is very probable that 

 this germ does not grow or multiply outside of the animal 

 body. 



Many authorities (Baumgarten, etc.,) claim that the gas- 

 tric juice will not destroy the tubercle bacillus. If infected 

 sputa be kept at a temperature of 158^* Fah. for ten minutes 

 the tubercle bacilli are destroyed. The germ in the same 

 material is destroyed in 20 hours if 3 per cent, of carbolic 

 acid is added ; the germ perishes in five minutes in iodo- 

 form-ether; it dies in ten minutes in a mercuric chloride 

 solution (1 to 1,000). According to Koch the tubercle ba- 

 cillus perishes in a few hours in direct sunlight, and in five 

 to seven days in diffuse daylight. This germ may remain 

 virulent in ordinary living rooms from two to ten months, 

 varying with the light, heat and the frequency of disinfec- 

 tion or cleansing of the room. An absolute heat of 158 de- 

 grees Fah. for fifteen minutes in meat and other tuberculous 

 masses, will kill the germs. Boiling for one-half hour is 

 always fatal to the tubercle bacilli. In springs, wells and 

 all forms of surface water, at ordinary temperature, the tu- 

 bercle bacilli may maintain their virulency indefinitely. 

 Non- sterilized water from rivers and surface wells may be 

 contaminated ; likewise public drinking troughs. Freezing 

 will not destroy the tubercle bacillus. Fermentation and 

 decomposition of organic materials, in which tubercle ba- 



