INFECTIOUS MASTITIS IN GENERAL 19 



The Local Condition. — We must here distin- 

 guish between the primary lesion and the subsequent 

 inflammation. 



Primary Lesion. — ^We distinguish between the quan- 

 tity or extent, and the quality or character of the primary 

 lesion. 



Quantity. — The primary lesion may be more or less 

 extensive. It may be circumscribed upon a greater or 

 smaller part of a quarter of the udder or it may be diffusely 

 spread over the entire quarter. 



Naturally it always begins by affecting a localized part 

 but can become diffuse through spreading of the infectious 

 organisms in a comparatively short time (a few hours, 

 days or weeks). 



The factors which may circumscribe the infection are 

 mechanical or biological in character. 



The mechanical inhibiting influences are the milk stream 

 and gravity. The infectious organisms must develop 

 against the current of the milk secretion, which is usually 

 a fairly effective obstacle to an extension of the infection. 

 Greater difficulty is experienced by the infectious organ- 

 isms in developing in the milk-ducts in the opposite direc- 

 tion to gravity. For this reason, therefore, they grow at 

 first in the horizontal milk passages on either side of the 

 teat bases, especially in the part behind the teats of the pos- 

 terior quarters and before the teats of the anterior quarters. 

 The progress upward is more difficult and more protracted. 



The inhibiting biological influences against the bacteria 

 are the leucocytes. 



If the organisms grow slowly phagocytosis usually pre- 

 vents spreading of the infection. 



The primary lesion more or less quickly produces an 

 inflammation in the region, with emigi'ation of leucocytes 

 which may mechanically prevent further infection. It cre- 

 ates a cell stopper against the infection, as it were. 



