CHAPTER II. 

 TUBERCULOSIS AND SYPHILIS. 



Local Tuberculosis. The site of primary invasion in tuber- 

 culosis is largely determined by anatomical factors. The 

 uninjured epidermis affords an efficient protection, so when 

 infection through the skin does occur it is in parts exposed to 

 free contact and to mechanical injury, such as the margin of the 

 nostril, the lip, and the angle of the eye. Tuberculosis of the 

 skin may follow trivial injuries, such as tattooing, hypodermic 

 injections, or scratches received during post-mortem examina- 

 tions. Another example of wound infection is the local tuber- 

 culosis which sometimes follows ritual circumcision. When 

 tuberculosis attacks the skin it is not always by direct 

 inoculation ; the primary focus of infection may be in a mucous 

 membrane close by, as occurs in some cases of facial lupus. 

 The skin may also be infected through the medium of its blood- 

 vessels, but for some reason this is rare, possibly because the 

 comparatively low temperature of the surface does not much 

 favour the growth of the bacillus. 



The digestive tract, like the skin, is exposed to direct infection, 

 and the parts most likely to suffer are those which are most 

 richly supplied with lymphoid tissue. The tonsils and the lower 

 part of the small intestine are peculiarly vulnerable on this 

 account. The tonsil, with its crypt-like structure, is not only 

 exposed to primary infection, but is often secondarily infected by 

 tuberculous sputum, and the same applies to the small intestine. 



The soft palate, which during swallowing and coughing serves 

 to shut off the posterior nares, is liable to primary infection by 

 the passage of tuberculous food and to secondary infection by the 

 forcible impact of phthisical sputum. 



The mouth, pharynx, and oasophagus are well protected by 



