METHODS AND CHANNELS OF INFECTION 671 



or down the oesophagus to the stomach and intestines. During the 

 ordinary inspiratory part of a respiration it is probable that micro- 

 organisms cannot pass directly into the alveoli of the lung as the 

 tortuous passage, the mucus and the cilia are fairly efficient barriers. 

 Bacteria may be inhaled directly into the finer bronchi and the alveoli 

 during forced inspiration such as that attendant upon hiccoughing and 

 sneezing. Infections of this kind occur in pneumonia, tuberculosis, 

 and influenza. Microorganisms frequently lodge on the membrane 

 of the trachea and are here taken up by the leucocytes and carried to 

 the lungs, bronchial lymph glands, and occasionally to other parts of 

 the body by the blood and lymph. It is probable that such a form of 

 infection occurs sometimes in pneumonia, tuberculosis and plague. 



Infectious microorganisms very frequently pass down to the 

 stomach and intestines. The mucous membrane of the stomach 

 is normally .very resistant to infection due to the hydrochloric acid 

 which is normally present in the gastric juice and which in normal 

 amount is distinctly antiseptic. It should be remembered that in 

 instances where the acidity of the stomach is lowered that .micro- 

 organisms will develop. All toxins with the exception of that of 

 B. botulinus of meat poisoning are destroyed by the gastric juice. 

 The intestines are less resistant to infection. It is here that the 

 causal microorganisms of typhoid fever, Asiatic cholera, chicken 

 cholera and dysentery and the various hemorrhagic septicemias find 

 their particular affinities. These bacteria enter or attach themselves 

 to the intestinal wall and in the case of cholera and dysentery this 

 is the only point of infection. The B. typhosus has occasionally 

 been known to enter at other places. This bacterium, however, com- 

 monly localizes in the lymphatic patches (Peyers) of the intestine, 

 and may enter the blood from this point. It should be noted that some 

 bacteria can pass through the wall of the intestine when it is seemingly 

 intact. This point has been repeatedly demonstrated in the case of 

 Bad. tuberculosis. 



The genital organs of the male and female are susceptible to in- 

 fection with microorganisms in certain instances. The M. gonorrhoea 

 of gonorrhoea and the Treponema pallidum of syphilis find their usual 

 portals of entry in the genital tract. They have, however, been known 

 to infect other parts of the body as the mouth, rectum, and the con- 

 junctiva. The etiological bacteria of gonorrhoea can penetrate the 



