RELATION OF BACTERIA TO DISEASE 16L 



when the tuberculous focus is in the wall of the intestine and 

 is discharging into it, or when the animal is swallowing ex- 

 pectoration coming from the lungs in which there are open 

 tuberculous lesions. In cases of anthrax, the bacteria escape 

 with the excreta after the organisms grow or come through 

 the mucous membranes. 



2. They escape with the secretions where the diseased 

 focus is discharging into the ducts of secreting glands. 



3. They escape with the pus from abscesses that are dis- 

 charging externally. 



4. When present, they escape with the blood taken by 

 insects. 



5. They are disseminated by dogs, foxes, buzzards and 

 other animals that serve as scavengers by eating the flesh and 

 organs of dead infected animals. 



Resistance of bacteria to external influences. An im- 

 portant feature in the spread of pathogenic bacteria is their 

 power to live after leaving the infected individual and before 

 there is opportunity to gain entrance to healthy ones. The 

 prevention of infectious diseases centers itself largely in the 

 control of the channels of dissemination and the channels 

 through which the disease producing bacteria gain entrance to 

 the body. 



Bacteria of wound infection. There is a large number 

 of bacteria that are able to produce more or less disturbance 

 by way of exciting an inflammatory process when they are 

 introduced into the animal tissues. As a rule these bacteria 

 are pyogenic micrococci and streptococci but occasionally 

 other species are found. These organisms gain entrance 

 through wounds either accidental or surgical in origin. The 

 character of the lesion does not indicate the species of bacteria 

 producing it, as much depends upon the virulence of the or- 

 ganism and the resistance of the host. The serous and 

 fibrinous exudates and the active spreading inflammations are> 

 more liable to be caused by streptococci than by M. pyogenes. 

 The occasional isolation of other bacteria that are very active- 

 in the production of spreading inflammations suggests the- 



