586 INFECTION AND IMMUNITY. 



Tuberculosis of the nose is uncommon. Infection 

 of the tonsils is not infrequent and probably is a 

 common cause of secondary tuberculosis of the cer- 

 vical lymph glands. Primary infection of the 

 pharynx sometimes occurs and large, coarse granu- 

 lations of this surface have been proved in some 

 cases to be of a tuberculous nature. Tuberculosis 

 of the pharynx and larynx, however, most often 

 arises from infection with tuberculous sputum. 



In the process of dust infection of the lungs, and 

 also by other means, many organisms lodge on the 

 mucous membranes of the nose, mouth, pharynx, 

 trachea and larger bronchi, but usually without 

 producing a tuberculous infection. On account of 

 the movement of the ciliated epithelium, tortuos- 

 ity of the nasal channels, excretion of the bacilli 

 with mucus, the conditions at these points are not 

 favorable for infection. 



Tuberculous ulcers of the esophagus and stom- 

 ach are very rare, as is primary tuberculosis of the 

 intestines. Secondary tuberculosis of the intes- 

 tines usually is caused by the infected sputum 

 which the patient swallows. Primary infection of 

 the genital organs may arise from direct contact. 



That tubercle bacilli have often been found on 

 the hands and finger nails of the sick as well as on 

 those who are intimately associated with them is a 

 significant fact in relation to the possibility of in- 

 fection by direct contact. 



From a given focus tubercle bacilli extend to 

 other structures in several ways. On more or less 

 theoretical grounds one speaks of "extension by 

 growth" of the organism into contiguous tissues. 

 The commonest method of extension, however, is 



