TUBERCULOSIS 47 



the pathogenic, and of the different types of the latter to one another 

 must await future investigations. 



Avenues of Infection. The most important of these lies in the 

 respiratory organs. The nose serves as a filter and its secretion is 

 germicidal. Besides, there is free exit for accumulations, and the ease 

 with which sneezing is induced by slight irritation and air can be 

 forced through it by blowing the nose, tends to keep this cavity clean. 

 The nose is seldom, probably never except in wounds or abrasions of 

 the mucous membrane, the seat of a primary tuberculous infection. It 

 may be secondarily involved in tuberculosis of the lungs. Mouth 

 breathing increases the chances of infection. The retronasal pharynx 

 is less easily kept clean and is more frequently the site of infection, 

 but this also is generally secondary. The tonsils frequently, even in 

 non-tuberculous persons, are found to contain tubercle bacilli. 

 Whether these glands do more than retain the bacilli is not known. 

 The larynx is more frequently the seat of primary infection, and is 

 involved sooner or later in about one-fourth the cases of pulmonary 

 tuberculosis. 



Infection of the trachea and large bronchi is rare. The primary 

 seat of most cases of pulmonary tuberculosis is in one of the apices 

 of the lungs. This is due to the fact that bacilli having reached these 

 localities are not easily dislodged. This is true of inhaled particles 

 of any kind and when these are hard and rough they cause slight 

 wounds which form suitable places for the entrance and growth of the 

 bacilli. This accounts for the greater susceptibility to tuberculosis of 

 those engaged in dusty occupations, especially marble cutters and 

 steel filers. 



The next most favorable avenue for tuberculous inoculation is 

 through the digestive organs. Carious teeth provide a port of entry 

 and the infection introduced in this manner finds its way into the 

 adjacent glands. Sore and raw gums due to deposits of tartar and 

 the fermentation of lodged particles of food, offer additional points 

 of entry not only for the tubercle bacillus but for other pathogenic 

 organisms. These facts emphasize the importance of oral hygiene, 

 which is greatly neglected in both children and adults. Tubercle 

 bacilli have been detected in carious teeth, in tartar and in the coating 



