UDDER-PYOBACILLOSIS 79 



Local Conditions. — The lesions produced in the udder 

 occur in proportion to the number of organisms which gain 

 entrance. The bacilli are taken up by the leucocytes in the 

 capillary blood, in wounds, or in the milk and deposited in 

 the stroma of the udder, where the leucocytes are finally 

 necrotized by the parasites. In many cases perhaps the 

 opposite condition takes place, that is, the bacilli are de- 

 stroyed and the infection prevented. The infection can 

 occur, however, by entrance of gi'eat numbers of bacteria, 

 that is, many bacteria; but still more leucocytes are de- 

 stroyed and the infectious organisms become superior to 

 the leucocytes. 



An inflammatory zone forms around these necrotic cells 

 (primaiy lesion) and outside of this zone of leucocytes a 

 capsule of connective tissue develops. Secondary nodules 

 are formed during the removal of the infectious organisms 

 by the leucocytes. All of these foci gradually enlarge with 

 subsequent atrophy of the tubules and finally ulceration 

 into the tubules or outward through the wound, if one be 

 present, or through the skin. 



Depending upon the point of entrance of the infection 

 the following forms may be distinguished, i.e., ( 1 ) primary 

 udder-pyobacillosis ; (a) udder-pyobacillosis through teat 

 infection; (b) udder-pyobacillosis through wound-infec- 

 tion. ( 2 ) Secondary or embolic udder-pyobacillosis. 



Primary udder-pyobacillosis usually occurs without 

 pyobacillosis of the lungs. It may, however, be present 

 along with the lung condition, in which case the latter may 

 be either primary or secondary (caused by blood-infection 

 induced by udder conditions) . 



Udder-pyobacillosis through teat infection usually 

 affects a single quarter, but can then reach other quarters 

 through infection, i.e., during milking. It starts around 

 the base of the teats and then spreads further sideways and 

 upward. 



