TUBERCULOSIS 41 



improved methods the disease can be recognized in most instances 

 while it is still an unmixed infection and amenable to proper treat- 

 ment. 



The behavior of the bacillus outside the animal body is a matter of 

 great importance in attempting the restriction of this disease. For- 

 tunately, under ordinary conditions, the tubercle bacillus does not 

 multiply outside the animal body. It is rapidly overgrown and starved 

 out by saprophytic organisms. It has been a parasite so long that the 

 range of temperature at which it will multiply is limited. Even in pure 

 cultures, protected from other organisms and provided with an abun- 

 dance of suitable food, it grows but slowly at a temperature only a 

 few degrees below that of the body. It needs oxygen and when the 

 supply of this element is short, growth is slow. 



However, the practical question is, How long will it retain vitality 

 and virulence outside the body? Multiplication as a saprophyte is 

 under ordinary conditions not at all probable, but how long will the 

 organism thrown off from the body in the sputum remain a source 

 of danger? This depends on many conditions. A mass of sputum 

 deposited on a glass plate and allowed to stand at ordinary room tem- 

 perature and in diffuse light may contain virulent bacilli for six 

 months. When the sputum is spread on a plate in a very thin layer 

 and submitted to the direct sunlight, only a few hours are necessary 

 to destroy its virulence; when only placed near a window, days are 

 necessary, and sputum deposited on carpets, rugs, bedding, handker- 

 chiefs, clothing, etc., may retain its virulence for months. Sputum 

 on walks and floors dries and is scattered by winds and drafts and 

 may be inhaled or deposited on food. The fly may carry the organism 

 to food. Heat immediately kills the tubercle bacillus when suspended 

 in water or milk on boiling. Lower temperatures must be maintained 

 for longer periods of time. According to Forster the following Centi- 

 grade temperatures must be continued for the periods mentioned in 

 order to be effective: 55 for four hours; 60 for one hour; 65 for 

 fifteen minutes; 70 for ten minute; 80 for five minute; 90 for two 

 minutes; 95 for one minute. 



Milk should be boiled at least three minutes to insure the destruc- 

 tion of this bacillus. In thoroughly baked or roasted meat the bacilli 

 are destroyed, but in the rare portions they may retain their vitality. 



