42 TUBERCULOSIS 



Dry heat must be carried to a higher degree or continued for a longer 

 time. Low temperatures are without effect. On account of their fat 

 and wax content tubercle bacilli are highly resistant to disinfectants. 

 Mercuric chlorid 1 :500 and 5 per cent, phenol (carbolic acid) are not 

 efficient in the sterilization of sputum even when the contact continues 

 for twenty-four hours. The ordinary gaseous disinfection of rooms 

 with formaldehyd is unreliable in case of infection with this bacillus. 

 Sputum from the tuberculous should be burned. 



The Bovine Bacillus. It has been shown, largely through the work 

 of Theobald Smith, that the human and bovine tubercle bacilli are not 

 identical. They show certain well-marked and characteristic differ- 

 ences in shape, size, rapidity and manner of growth, in response to 

 stains and in pathogenicity. Some years ago Koch announced that in 

 the crusade against tuberculosis in man we can afford to neglect milk 

 as a causative agent. This assertion led to much investigation into 

 the resemblances and differences between these varieties of the 

 tubercle bacillus. With the cultural and tinctorial differences we need 

 not concern ourselves at present. 



Cattle are highly resistant to infection with the human variety. 

 Cattle have been fed for months with large quantities of the human 

 bacillus without developing an infection. Some of the material 

 accumulates in the mesenteric glands and undergoes calcification but 

 the animal does not develop tuberculosis. In ordinary infecting doses, 

 intravenous injection is without effect. With larger amounts the ani- 

 mal may be poisoned as might result from similar treatment with any 

 one of a number of foreign proteins. The human bacilli when thus 

 injected into a cow may live for months and may be detected in the 

 milk. Intraperitoneal injections are without effect and the same is 

 true of those given subcutaneously, except that large quantities may 

 cause a local inflammation and this may extend to neighboring glands. 

 Inhalation is without effect. It is safe to say that cattle are free from 

 the possibility of being infected with tuberculosis from man. 



The guinea-pig is highly susceptible to both varieties, but the 

 bovine kills it quicker. The human variety is uncertain in its action 

 on rabbits. If it develops at all, it does so slowly and as a rule 

 requires some weeks and possibly months to cause death. On the 



