UDDER-PYOB ACILLOSIS 77 



but many pyogenes bacilli which were for the most part 

 within the cells. The animal was now slaughtered. 



Autopsy. — The infected quarter was moderately swol- 

 len, irregular, nodular and of firm consistency. The in- 

 cision was smeared with a thick yellowish-green pus. The 

 cut surface was even, yellowish-gray and firm. The lobuli 

 showed no milk points, but showed pus points distinctly. 

 Upon pressure yellow pus cylinders were expressed. 

 Externally seven suppurative foci were observed which 

 ranged in size from a hazelnut to a walnut. They contained 

 yellowish-green cheesy pus and were surrounded by a white 

 thick, firm connective-tissue capsule. Numerous milk-ducts 

 formed thick firm cords which on cross section presented 

 yellowish-green pus centres and were surrounded by a 

 white, thick, firm layer of connective tissue ( fistula forma- 

 tion) . The yellowish-green pus contained a great number 

 of small thin Gram positive pyogenes bacilli. 



Both of these experiments are good examples of infec- 

 tion through transportation of the infectious organism 

 by the leucocytes. The infected milk is quickly freed from 

 the organisms by resorption, that is, in these cases the leuco- 

 cytes pick up the organisms and carry them away. 



In the lymph-vessels a few of these phagocytes are 

 destroyed by the living bacteria which they contain and 

 these liberated organisms induce a stroma-infection which 

 finally terminates as a secondary milk-infection by per- 

 forative ulceration of the milk-ducts. 



Bacillus pyogenes so restrains itself that it simulates a 

 saprophyte and leucocytes may pick it up and re-enter the 

 vessels, where later it manifests its parasitic nature and 

 then destroys these cells. It is therefore insidious in its 

 action. It might be classed as a cell parasite instead of a 

 fluid parasite because of this action toward cells. 



In the first experiment the action of the bacilli was 

 slower and less widespread, because the alactiferous (dry) 



