94 Agricultural Bacteriology. 



most frequently introduced into wounds with the dirt at 

 the time the wound is made. A wound that does not 

 bleed freely, or one that is not cleaned thoroughly, is 

 more likely to prove a source of trouble than a cut which 

 bleeds freely. The bites of insects are, with certain dis- 

 eases, the way in which the organism is introduced into 

 the body. Wounds may be on the exterior of the body, 

 or on the interior surface, as in the mouth, stomach, or 

 intestines. 



The alimentary tract is the portal of entrance for some 

 disease producing-bacteria, especially for those that pro- 

 duce those diseases known as intestinal diseases, as hog 

 cholera and chicken cholera. In these diseases the bac- 

 teria grow in the intestines. In other diseases the causal 

 organisms are able to pass through the walls of the in- 

 testines and thus get into the blood and lymph to be 

 carried to various parts of the body. 



The air passages and lungs form a third portal of en- 

 trance. The bacteria in the dust of the air lodge in the 

 various parts of the air passages or in the lungs. Influ- 

 enza, pneumonia, and tuberculosis may be acquired in 

 this way. 



Exits of bacteria from the body. The bacteria once 

 in the body grow in various parts, depending on the na- 

 ture of the disease. In most diseases they pass, in 

 greater or less numbers, from the body of the animal be- 

 fore death occurs. They are thrown off in the manure in 

 the case of intestinal diseases, such as hog cholera ; in the 

 urine ; in the sputum, as in tuberculosis and pneumonia ; 

 in the contents of boils and ulcers, as in glanders and py- 

 ogenic troubles; in the milk when the udder is diseased, 

 as in garget and tuberculosis, and in the blood drawn 

 from the body by sucking insects. After death by the 



