ACUTE MAMMITIS. 573 



ACUTE MAMMITIS. 



Causation. The general cause of acute mammitis, like that of 

 chronic mammitis, is infection by pathogenic organisms, whether such 

 organisms enter by the usual natural path, viz., the galactophorous 

 sinus and excretory apparatus, by the lymphatic path, owing to some 

 accidental injury, or, again, by the blood circulation. 



Infection of the lymphatics undoubtedly plays a part in superficial 

 and interstitial inflammations, and it is proved that certain micro- 

 organisms may pass into the milk, as it has been proved that they 

 pass through the kidney. 



But if infection is the determining cause, certain secondary favour- 

 ing influences must not be overlooked. 



Thus lactation is an almost indispensable condition. It is true 

 that some cases of mammary inflammation apart from lactation have 

 been described, but they have been the result of violence, accidental 

 or mechanical. 



Accumulation of milk in the udder (overstocking) has unquestion- 

 ably a certain influence in the large milk-yielding animals, not because 

 it directly produces inflammation, but because milk then escapes spon- 

 taneously ; and as the udder cannot be entirely evacuated without 

 external assistance, the entrance is kept permanently open for the 

 passage of germs, which are freely transferred to the teat from the 

 litter and surrounding objects. 



Cold, or rather chills, also act in a complex manner, particularly 

 by disturbing vaso-motor control. Diflerent forms of mechanical 

 violence, such as blows, crushing strains, wounds, etc., may immediately 

 and directly set up local or general inflammation. 



Bacteriological investigation has proved that numerous and varied 

 micro-organisms can be found in the milk or interstitial exudates in 

 cases of mammitis, but only a few special forms have been proved to 

 be specific : streptococcus of contagious mammitis of milch cows, and 

 micrococcus of contagious gangrenous mammitis of ewes (Nocard). 



Pathology. The pathogenic results produced by infective organisms 

 depend on their number and power of reproduction, and on the activity 

 of their life products. 



The most immediate and regular result of acute mammary infec- 

 tion is coagulation of the milk within the udder by decomposition of 

 the lactose, and the formation of lactic or even of butyric acid. The 

 acini and excretory canals are dilated by coagula, and can no longer 

 expel their products of secretion, so that the colonies of micro-organisms 

 develop there in full security. The active epithelial cells undergo 

 granular degeneration and disappear, whilst the walls of the glands 



