238 Manual of Veterinary 3Ilcrohlotogy. 



sis lias not been confirmed ; the numerous tests 

 which have ah'eady been made have shown that tuber- 

 culin, instead of exerting a curative efiect, may be 

 positively harmful and cause the extension if not the 

 generalization of the disease. The reagent is, in 

 reality, without effect on the bacillus, whilst the in- 

 flammatory reaction which develops around the 

 tubercles causes an aggregation of leucocytes which, 

 becoming charged with microbes, transport these to 

 points outside of the original lesion where they can 

 incite new centers of disease ; this inflammatory re- 

 action can, further, become directly harmful when 

 the tubercles are numerous and occupy a large ex- 

 tent of an important organ. 



Etiology and pathogeny. — Contamination with tuber- 

 culosis is most frequently indirect, but may also take 

 place in a direct manner. 



Instances in which physicians and veterinarians 

 have contracted the disease in making autopsies of 

 diseased men or aiiimals are incontestible, though 

 fortunately rare. The virus inoculated through a 

 wound, in such cases, occasions first of all a more or 

 less limited cutaneous tuberculosis which may later 

 become generalized. 



Transmission of the disease from mother to foetus 

 constitutes another example of immediate contagion. 

 This mode of transmission, although now placed be- 

 yond doubt both for animals and mankind, is actu- 

 ally of rare occurrence; the tubercle bacillus is in 

 reality confined to the specific lesions and only ex- 

 ceptionally circulates in the blood ; moreover, it has 

 not yet been demonstrated that it is capable of pass- 

 ing through the villosities of the intast chorion, 



