CHAPTER V 



PATHOGENIC MICROBES — INFECTION 



Origin. — Specificity — Virulence. — How virulence may have been acquired 

 — Evolution of microbes — The ' para ' and the ' pseudo ' forms — 

 Diminution and augmentation of virulence — Pasteur and attenuation of 

 the virus. 



Infection. — The conflict between the microbe and the body — Methods 

 — of transmission — Latent microbism — Germ-carriers — -The number of 

 microbes sufficient to produce infection — Microbial associations — Paths 

 of penetration and inoculation — The role of the intestine — Seats of 

 election and susceptible cells — Incubation. 



Origin : Specificity : Virulence. 



The idea of pathogenic microbes arose as a result of Pasteur's 

 labours on fermentation. 



For years the bacteridium had been seen in the blood of 

 anthrax animals without giving rise to the thought that these 

 microscopical rods were the cause of the illness. After the 

 discovery of the bacillus of butyric fermentation, Davaine 

 considered that the bacteridia were the cause of anthrax as a 

 sort of peculiar fermentation having for its subject the body of 

 an animal. 



We do not yet know the pathogenic microbes though they 

 certainly exist in small-pox, in vaccinia, in measles, in 

 scarlatina, in mumps, and in hydrophobia. That of syphilis 

 remained unknown up to 1905. Pasteur was the first to handle 

 invisible microbes with sufficient confidence to discover a 

 method of vaccination. His discoveries in hydrophobia aroused 

 researches on the so-called invisible microbes. A nervous 



107 



