Physiology of Pathogenic Microbes. 79 



exterior ; this elimination is more or less complete 

 according to the case. 



When the germs aredeeply situated their expulsion 

 may still take place through certain glands — the kid- 

 neys, the salivary glands (rabies), the liver (symptom- 

 atic charbon). The elimination of infectious germs 

 by way of the kidneys has been observed for a large 

 number of diseases; generally, if not always, it is 

 the consequence of the irritation which the microbes 

 or their products exert upon the organ. Many mi- 

 crobic diseases, in fact, are accompanied by nephritis. 

 The more or less complete desquamation of the 

 secretory epithelium, and the vascular troubles which 

 then supervene account for the passage of the mi- 

 crobes. 



If the elimination of the figured agents of the in- 

 fectious diseases demands conditions somewhat com- 

 plex, the rejection of their secretions is more readily 

 accomplished, since these substances are dissolved in 

 the liquid media of the economy. Their filtration 

 takes place especially through the kidneys; their 

 presence in the urine has been established; but they 

 may also transude from the various other natural 

 emunctories. 



4. 3Iodijications of virulence — The bactericidal prop- 

 erty of the humors has the power of attenuating the 

 virulence of pathogenic microbes. Inversely, the 

 absence of this property may occasion an increase 

 of this virulence. Thus, the virulence of a given 

 microbe may become increased or diminished by 

 passing through a series of individuals of the same 

 species : rouget of the pig becomes more active when 

 it is made to pass through the pigeon or the rabbit; 



