DESCRIPTIONS OF PATHOGENIC BACTERIA. 149 



cussion of etiology. For the present, a pre- 

 liminary survey is sufficient. 



A primary distinction is often made between 

 the truly infectious organisms, organisms 

 namely which, when introduced in small num- 

 bers into the body of men or the lower ani- 

 mals, can increase there abundantly ; the poison- 

 ous or toxic bacteria which, when introduced 

 even in small numbers into the body of the host, 

 produce poison ; and the phenomenon of in- 

 toxication or poisoning which is caused only 

 by the direct incorporation of quantities of toxin. 

 Virulence may be said in general to be the 

 power to grow or produce poisons in the body. 



Some bacteria produce ill effects by poisons 

 which they generate outside of the body dur- 

 ing the course of the decomposition of dead 

 organic material, the organisms themselves not 

 being able to grow in the animal body. A. 

 group of facts bearing on this point was first 

 securely established by Panum I in 1874. To 

 this class belong many of the bacteria of putre- 

 faction. In some instances after the body has 

 been weakened by the poisons, these putre- 

 factive bacteria may become able to multiply 

 within the organism. 



B. Proteus, discovered by Hauser 2 in 1885, 



1 Virchow's Archiv, LX., p. 358. 



2 Ueber Faulnissbakterien, 1885. 



