242 PATHS OF ENTRANCE OF PATHOGENIC ORGANISMS 



pneumonic plague in man, lobar and bronchopneumonias 

 and influenza in man and animals, some cases of glanders 

 and tuberculosis). On the other hand, the fact that the 

 Eberthella typhi and Escherichia coli may cause pneumonia 

 when they evidently have reached the lung from the intes- 

 tinal tract, and the experimental evidence of lung tubercu- 

 losis above mentioned show that this route cannot be excluded 

 in inflammations of the lung. 



D. Alimentary Tract.— The alimentary tract affords the 

 ordinary path of entrance for the causal microbes of many 

 of the diseases of animals and man, since they are carried 

 into tlie body most commonly and most abundantly in the 

 food and drink. 



(a) The stomach is rarely the seat of local infection, even 

 in ruminants, except as the result of trauma. The character 

 of the epithelium in the rumen, reticulum and omasum in 

 ruminants, the hydrochloric acid in the abomasum and 

 in the stomachs of animals generally are usually sufficient 

 protection. Occasionally anthrax "pustules" develop in the 

 gastric mucosa. (The author saw nine such pustules in a 

 case of anthrax in a man.) 



(6) The intestines are frequently the seat of localized 

 infections, as various "choleras" and "dysenteries" in men 

 and many animals, anthrax, tuberculosis, Johne's disease. 

 Here doubtless enter the organisms causing "hemorrhagic 

 septicemias" in many classes of animals and numerous 

 others. These various organisms must have passed through 

 the stomach, and the question at once arises. Why did the 

 HCl not destroy them? It must be remembered that the 

 acid is present only during stomach digestion, and that 

 liquids taken on an " empty stomach" pass through rapidly 

 and any organisms present are not subjected to the action 

 of the acid. Also spores generally resist the acid. Other 

 organisms may pass through the stomach within masses of 

 undigested food. The fact that digestion is going on in the 

 stomach of ruminants practically all the time may explain 

 the relative freedom of adult animals of this class from 

 "choleras" and "dysenteries." 



