310 A MANUAL OF BACTERIOLOGY 



added was rendered innocuous by a momentary heating 

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

 perature of 65 C. and over is probably rapidly fatal to 

 the tubercle bacillus, so that milk which has been pas- 

 teurised (i.e. heated to 68-70 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 to 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, 1-1000, 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 Chap. XXI.) 



Pathogenesis, etc. Man is, unfortunately, only too fre- 

 quently attacked with tuberculosis, the manifestations 

 of which tend to differ somewhat at different age periods. 

 Thus, in the very young, general miliary tuberculosis, 

 tuberculous meningitis, and tuberculous disease of the 

 peritoneum, intestine, and mesenteric glands (tabes mesen- 

 terica) are the commonest ; in older children, up to the 

 age of puberty, the lymphatic glands, especially in the 

 neck, joints and bones, and the skin (lupus) are mostly 



