TUJ-: BACILLUS OF TUBERCULOSIS 297 



on account of their location they are greatly protected. Most of the bacilli 

 are caught upon the nasal or pharyngeal mucous membranes. Only 

 a small percentage can find their way to the larynx and trachea, and 

 still less to the smaller bronchioles. From the examination of the lungs 

 of miners as well as from experimental tests there is no doubt but that 

 some of the bacilli find their way into the deeper bronchi. The deeper 

 the bacilli penetrate the more unlikely that they can be cast out. The 

 healthy lung tissue usually destroys these bacilli. The nasal cavities 

 are rarely affected with tuberculosis, but more often the retropharyn- 

 geal tissue. Tuberculosis of this tissue as well as that of the tonsils is 

 apt to give rise to infection of the lymphatic glands of the neck. It 

 is believed that just as bacilli may pass through the intestinal walls to 

 infect the mesenteric glands so bacilli may, without leaving any trace, 

 pass through the tonsils to the glands of the neck. It is now well 

 established that infection taking place through various channels may 

 find its way to the lungs and excite there the most extensive lesions. 



TUBERCULOSIS OF LARYNX. Primary infection of the larynx is rare. 

 Secondary infection is fairly common. The region of the vocal cords 

 and the interarytenoid space are the special sites attacked. 



INFECTION BY INHALATION OF DRIED AND MOIST BACILLI. The 

 most common mode of infection is by means of tuberculous sputum, 

 which, being coughed up by consumptives, is either disseminated as a 

 fine spray and so inhaled, or, carelessly expectorated, dries and distributes 

 numerous virulent bacilli in the dust. As long as the sputum remains 

 moist there is no danger of dust infection, but only of direct contact; 

 it is only when it becomes dry, as on handkerchiefs, bedclothes, and the 

 floor, etc., that the dust is a source of danger. 



A great number of the expectorated and dried tubercle bacilli 

 undoubtedly die, especially when exposed to the action of direct 

 sunlight; but when it is considered that as many as five billion 

 virulent tubercle bacilli may be expectorated by a single tuberculous 

 individual in twenty-four hours, it is evident that even a much smaller 

 proportion than are known to stay alive will suffice in the immediate 

 vicinity of consumptives to produce infection unless precautions are 

 taken to prevent it. The danger of infection is greatest, of course, in 

 the close neighborhood of tuberculous patients who expectorate pro- 

 fusely and indiscriminately that is, without taking the necessary 

 means for preventing infection. There is much less danger of infection 

 at a distance, as in the streets, for instance, where the tubercle bacilli 

 have become so diluted that they are less to be feared. In rooms the 

 sputum is not only protected from the direct sunlight, but it is con- 

 stantly broken up and blown about by the walking, closing of doors, 

 etc. In crowded streets on windy days infected dust must sometimes 

 be in the air unless the expectoration of consumptives is controlled. 



Exhaustive experiments made by many observers have shown that 

 particles of dust collected from the immediate neighborhood of con- 

 sumptives, when inoculated into guinea-pigs, produce tuberculosis 

 in a considerable percentage of them; whereas, the dust from rooms 



