68 Manual of Veterinary Microbiology. 



oculation of a minimum quantity of certain germs 

 confers immunity, whilst a larger dose produces the 

 fatal disease (gangrenous septicjjemia, symptomatic 

 charbon). 



7. Irijiuenee of microhic associations. — The suscepti- 

 bility to an experimental disease is increased by in- 

 jecting, at the beginning of this disease, a consider- 

 able amount of the soluble products coming from the 

 microbe inoculated (Bouchard). This fact has been 

 established for the charbon bacteridium, fowl cholera, 

 the staphyloccus aureus, bacillus prodigiosus, the ba- 

 cillus of symptomatic charljon, the pyocyanic bacil- 

 lus, etc. This is the more striking since the injection 

 of the same products without microbes often confers 

 immunity. Here, on the other hand, it aggravates 

 the trouble or renders it possible, by overcoming the 

 natural or acquired immunity. The mode of action 

 of these substances consists, in this case, in the ob- 

 struction which they oppose, by paralyzing the vaso- 

 dilator nerves, to the diapedesis and phagocytosis 

 which the germs of the disease naturally excite when 

 they are inoculated to vaccinated subjects, or those 

 which are naturally refractory. 



The adjuvant action that the microbic secretions 

 exert in association with the microbe from which 

 they come, may also be manifested in association with 

 other germs ; thus, the natural immunity of the rab- 

 bit against symptomatic charbon is obliterated if we 

 inject to this animal, at the same time with the char- 

 bon bacteria, a sterilized culture of the staphylococcus 

 aureus, or micrococcus prodigiosus. 



The same interpretation is applicable to the predis- 

 posing or aggravating influence that a previous or 



