52 3Ianual of Veterinary 3Iicrohiology. 



case of charbon and tuberculosis, for example. It is 

 therefore necessary to carefully destroy tliese bodies. 



m. 3Iodes of contagion. — Ways of penetration of patho- 

 genic microbes. 



Those germs which are exciters of disease, after 

 having multiplied in the bodies of the first infected 

 animals, may be transported to other animals and 

 thus propagate the disease. This transference of the 

 germs of a disease from a sick to a healthy individual 

 constitutes contagion. 



1. Modes of contagion. A microbic disease will the 

 more surely be communicated, the contagion will have 

 greater opportunity of taking effect, in proportion to 

 the number of the germs emitted by the diseased. A 

 superficially situated disease will be more readily trans- 

 missible, other things being equal, than a deep seated 

 one ; a disease with lesions of large extent will be 

 more easy to communicate than one in which these 

 are less extensive. The greater or less duration of the 

 resistance of the virus to the natural agents of destruc- 

 tion is also a condition upon which depends the aug- 

 mentation or diminution of the contagion-begetting 

 power of the virus. 



The transference of pathogenic germs from a 

 diseased subject to a healthy subject — contagion — may 

 be direct or immediate, that is, the healthy subject ob- 

 tains the germs of the disease from the diseased ani- 

 mal itself, or it may be indirect or mediate, the healthy 

 individual receiving the microbes eliminated by the 

 diseased, through the intervention of external media. 



Direct or immediate contagion. — Of this we have to 

 distinguish two cases according as the transmission 



