Pathogenesis 713 



of these facts teaches us that visits to consumptives should not be 

 prolonged; that no one should remain continually in their presence, 

 nor habitually sit within 2 meters of them; also that patients should 

 always hold a handkerchief before the face while coughing. The 

 rooms occupied by consumptives should also be frequently washed 

 with a disinfecting solution; 



Probably all of us at some time in our lives inhale living virulent 

 tubercle bacilli, yet not all suffer from tuberculosis. Personal 

 variations irfpredisposition seem to account in part for this, as it has 

 been shown that without the formation of tubercles virulent bacilli 

 may sometimes be present for considerable lengths of time in the 

 bronchial lymphatic glands — the dumping-ground of the pulmonary 

 phagocytes. 



In order that infection shall occur, it does not seem necessary that 

 the least abrasion or laceration shall exist in the mucous lining of 

 the respiratory tract. 



Infection also commonly takes place through the gastro-intestinal 

 tract from infected food. Present evidence points to danger from 

 tubercle baciUi in the milk of cattle affected with tuberculosis. 



The ingested bacilli may enter the tonsils and be carried to the 

 cervical lymph-glands, but seem more commonly to reach the in- 

 testine, from which they enter the lymphatics, sometimes to produce 

 lesions immediately beneath the mucous membrane, sometimes 

 to invade the more distant mesenteric lymphatic glands, but more 

 frequently to enter the thoracic duct and then through the venous 

 system find their way to the lungs. Passing this barrier they may 

 distribute through the arterial systemic circulation. The entrance 

 of tubercle bacDli into the systemic circulation with subsequent 

 deposition in the brain, bones, joints, etc., explains primary lesions 

 of these tissues. 



Koch* beUeved that human beings are infected only by bacilli 

 from other human beings, and his paper upon this subject has 

 stimulated extensive experimentation on the problem. Most 

 authorities beUeve both human and bovine baciUi to be equally 

 infectious for man. Behringf believes that nearly all children be- 

 come infected by ingesting tubercle bacilli in milk, though a certain 

 predisposition i| necessary before the disease can develop. 



Infection also occasionally takes place through the sexual appara- 

 tus. In sexual intercourse tubercle bacilli from tuberculous testicles 

 can enter the female organs, with resulting bacillary implantation. 

 Sexual infections are usually from the male to the female, primary 

 tuberculosis of the testicle being more common than of the uterus 

 or ovaries. 



Wounds are also occasional avenues of entrance for tubercle 



* "International Congress on Tuberculosis," London, 1901, and Washington, 

 1908. 

 t "Deutsche med. Wochenschrift," 1903, No. 39. 



