62 AIDS TO BACTERIOLOGY 



Channels of Infection. The sputa of consumptives are 

 almost certainly responsible for most infections. The 

 tubercle bacillus is, for a non-sporing organism, tenacious 

 of life, and when sputum is allowed to dry, especially 

 when protected from light and air, may easily be dis- 

 seminated in dust. In the acts of coughing, sneezing, and 

 talking, minute droplets of fluid are disseminated. Fliigge 

 has shown that these droplets may remain in the air for 

 some time, and also that, when from consumptives, they 

 often contain tubercle bacilli. The inhalation of either 

 tubercle-laden dust or droplets of saliva from consump- 

 tives must be regarded as a standing menace. Infection 

 may take place through the alimentary tract, especially 

 in infants, by the ingestion of tuberculous milk or meat. 

 Flies can carry the disease. A phthisical patient may 

 swallow his own sputum, and thus infect his alimentary 

 tract. Von Behring considers that tubercle bacilli taken 

 in milk during infancy may remain dormant for years, 

 and then set up infection. Accidental inoculations 

 through the skin with tuberculous material, principally 

 the result of post-mortem examinations (' pathologists' 

 warts '), are seldom serious. Lupus is presumably acquired 

 by inoculation through a wound or abrasion of the skin. 



Hamburger and Schlossmann practically agree that 

 90 per cent, of all children up to the completed twelfth 

 year are infected. 



Autopsy statistics show tuberculous lesions in 58 per 

 cent, of adults according to Beitzke. Other statisticians' 

 figures run up to 90 per cent, and more. 



Pathogenesis. Scarcely any portion of the human 

 frame is immune to tubercle. Whooping-cough, pneu- 

 monia, typhoid, measles, influenza, diabetes, and syphilis, 

 predispose to the disease, as do also intemperance, poverty, 

 uncleanliness, overcrowding, and lack of ventilation. 

 Trades in which operatives are exposed to dust of an 

 irritating kind, which are carried on in overcrowded, 

 hot, or badly-ventilated rooms, in which workers adopt 

 a cramped posture, or in which exposure to quick alterna- 

 tions of temperature is frequent, show a heavy mortality 

 from the disease. 



The disease is not hereditary in the true sense of the 

 word. An infected child of a tuberculous mother is gene- 

 rally the subject of postnatal infection. Nevertheless, 



