256 BACTERIA IN INFECTIOUS DISEASES. 



wall of inflammatory exudation is established ; 

 and we find the subcutaneous connective tissue 

 diffusely infiltrated with serum which swarms 

 with the parasite. 



The failure to restrict the inroads of the para- 

 site may not be due alone to its power of rapid 

 multiplication. It is not improbable that some 

 poison is produced, during its active growth, which 

 lowers the vital resistance of the tissues and pre- 

 vents the occurrence of conservative adhesive in- 

 flammation. And it may be that the true expla- 

 nation of the immunity afforded by a mild attack 

 of an infectious germ-disease is to be found in an 

 acquired tolerance to the action of a chemical poi- 

 son produced by the micro-organism, and conse- 

 quent ability to bring the resources of nature to 

 bear to restrict invasion by the parasite. 



In the infectious disease known as hospital gan- 

 grene, circumstances relating to the origin, nature, 

 and treatment of the malady make it seem ex- 

 tremely probable that some species of bacterium, 

 ordinarily harmless, develops pathogenic proper- 

 ties as the result of an unusually favorable environ- 

 ment, and becomes the infecting agent, which, by 

 invading the enfeebled tissues, causes the rapidly 

 extending necrosis which is characteristic of this 

 frightful malady. This disease is developed de novo 

 in the surgical wards of hospitals, where numerous 

 patients, with profusely discharging wounds, are 

 brought together. Like its congeners, erysipelas 

 ;iiid puerperal fever, it is prevented by cleanliness 



