354 MANUAL OF BACTERIOLOGY. 



in four hours, at 60° C. in 30 minutes, at 65° C. in 15 minutes, 

 at 70° C. in 10 minutes, at 80° C. in five minutes, at 95" C. in 

 one minute. These temperatures are of importance in the_ 

 matter of the sterilization of milk, since it is important that 

 milk should be heated as little as necessary. Theobald 

 Smith showed that the scum which forms on the surface of 

 milk when it is heated-protects the tubercle bacilli which are 

 in the scum from the effects of the heat. Sunlight destroys 

 the bacilli quickly, but in practice the protective coating of 

 sputum or other material may interfere with the action of the 

 sunlight. In fact the piotection afforded by the sputum may 

 operate in all cases where the bacilli are sought to be destroyed. 

 It is not destroyed always by the gastric juice as is seen in those 

 cases referred to below in which the bacilli are found in the 

 feces of persons affected with phthisis, and who swallow their 

 sputum. It has furthermore been shown by direct experi- 

 ment, as well as by the occasional occurrence of primary 

 intestinal tuberculosis, however rare, this may be compara- 

 tively speaking. In fact the view that the bacilli are not 

 destroyed by the gastric juice is the basis for Behring's con- 

 tention that all forms of tuberculosis are acquired by ingestion 

 of the bacilli. They are destroyed in sputum by carbolic acid 

 in the proportion of equal parts of a five per cent, solution of 

 the carbolic acid to the amount of sputum. The fumes from 

 4 pounds of burning sulphur to each 1000 cubic feet of air 

 space kills the tubercle bacillus in 8 hours provided the 

 bacilli are freely exposed and the atmosphere is kept moist.* 

 Formaldehyde is quicker but not more efficient in the propor- 

 tion of 10 ounces of formalin to 1000 cubic feet of space.f 



It is not known to grow, except in artificial cultures, outside 

 of the animal body. It is the cause of tuberculosis in man. 

 It produces tuberculosis in apes, cows, hogs, sheep, horses, 



*Park. hoc. cit. p. 200. 

 '{Ibid. 



