62 Manual of Veterinary 3Iicrohiology . 



This mechanical influence, however, seems to be 

 much the least important. The soluble substances — 

 diastases and ptomaines — secreted by the microbes 

 possess very active properties and to these we ascribe 

 the genesis of most of the manifestations of the in- 

 fectious diseases. 



Microbic diastases, as we have already said, repre- 

 sent the digestive juices of the microbes; they can 

 therefore act chemically upon the substance of the 

 tissues, provoking hydrations and chemical decom- 

 positions, and thus lead to the liquefaction, softening, 

 and even mortification of these tissues. These dis- 

 solutions are sometimes preceded by a sort of coagu- 

 lation (coagulation necrosis). 



The soluble substances — diastases and ptomaines — 

 may possess phlogogenic properties; in this case 

 they develop, of themselves alone, all the inflamma- 

 tory phenomena which follow the inoculation of the 

 microbes from which they come. They excite swell- 

 ing, proliferation, and fatty, hyaline, or waxy de- 

 generation of the elements, dilatation of the vessels, 

 exudation of products more or less plastic, sometimes 

 active diapedesis of the white blood corpuscles and 

 even extravasations. The pneumobacillus liquefaciens 

 bovis, isolated by Arloing from the lesions of bovine 

 contagious pleuro-pneumonia, secretes a diastase 

 which excites inflammatory cedemas recalling those 

 of the disease itself. The staphylococcus pyogenes 

 aureus produces a diastase and a ptomaine which are 

 phlogogenic and pyogenic. 



The local alterations which supervene in conse- 

 quence of the Introduction of certain germs into the 

 tissues sometimes depend, at least in part, on the 



