THE TUBERCLE BACILLUS 377 



found that milk to which powdered dried sputum had 

 been added was rendered innocuous by a momentary 

 heating to 67-68 C. These experiments indicate that a 

 temperature of 65 C. and over is probably rapidly fatal 

 to the tubercle bacillus, so that milk which has been 

 pasteurised (i.e. heated to 65-70 C. for twenty to thirty 

 minutes) may be regarded as quite safe. Experiments 

 by the Royal Commission on Tuberculosis with virulent 

 tuberculous milk gave somewhat irregular results ; in 

 one instance heating to 65 C. for two and a half minutes 

 rendered the milk innocuous, in another instance after five 

 minutes at 70 C. it was slightly virulent, but twelve 

 minutes at the same temperature rendered it inert. (See 

 also section on " Milk.") Foulerton found that emulsified 

 tuberculous material from tuberculous guinea-pigs did 

 not lose its power of infecting unless heated at 70 C. or 

 over for ten minutes. 



The tubercle bacillus offers considerable resistance to 

 the action of antiseptics and germicides. Yersin found 

 that it was killed by 5 per cent, carbolic acid in thirty 

 seconds, by 1 per cent, in one minute, by absolute alcohol 

 in five minutes, and by mercuric chloride, 1-1,000, in ten 

 minutes. Crookshank found that tuberculous sputum 

 mixed with an equal volume of 5 per cent, carbolic was 

 rendered innocuous in a few minutes, and this without 

 any special precautions as to breaking up the masses. 

 For disinfecting sputum mercuric chloride is unsuitable. 

 (See also " Milk " in Chap. XXI.) 



Pathogenesis , etc. Man is frequently the subject of 

 tuberculosis, the site and nature of the manifestations of 

 which tend to be different at different age periods. In 

 the very young, general miliary tuberculosis, tuberculous 

 meningitis, and tuberculous disease of the peritoneum, 

 intestine, and mesenteric glands (tabes mesenterica) are the 

 commonest ; in older children, up to the age of puberty, 



