MAMMITIS OR MASTITIS 705 



acini are swollen and infiltrated, and compress, or even efface, the proper 

 substance of the gland, as well as the vessels of the part. It is this 

 swelling and infiltration which causes the tumefaction of the mammie ; 

 though the inflammation of the proper gland-tissue will bring about the 

 same results. Retention of the milk is caused by the inflammatory in- 

 filtration of the connective tissue surrounding the milk-ducts and canals. 

 When inflammation has gone on to suppuration, we find, on section of 

 the affected gland, the gland-tissue more or less occupied by large and 

 small abscesses, adjoining healthy connective tissue ; these abscesses 

 may be isolated, or communicate with each other and form one large 

 irregular cavity. Sometimes there is necrosis of the ligamentous bands 

 which form the principal septa between the glands, and in this way are 

 produced fistulae or secondary abscesses, which may open externally or 

 into the milk sinuses. These latter are generally lined with a large 

 number of cylindrical epithelium ; in severe cases their walls are thick- 

 ened and of a dark color, their cavity, as well as that of the teat, being 

 dilated with the altered fluid. The matter in the abscesses varies ex- 

 ceedingly in its composition. Along with cylindrical epithelium are 

 blood-corpuscles, fat-crystals, fragments of yellow elastic tissue, colos- 

 trum corpuscles, and an extraordinary quantity of micrococci of various 

 shapes. 



The interlobular connective tissue is thickened, dense, and like ten- 

 don or cartilage (sclerosis). The gland tissue itself has, instead of a 

 yellow tint, a marbled aspect ; in chronic cases calcareous salts may 

 even be found in the textures. 



When circumscribed gangrene has occurred, and elimination of the 

 diseased part is accomplished, the dead mass may weigh as much as five 

 or six pounds in the Cow ; it is somewhat regularly oval, but rather flat- 

 tened and discoid in the Mare ; the color is a light or pale yellow, and 

 in consistence it is pulpy but not elastic, and the finger cannot be easily 

 passed into its substance ; traces of its lobulated structure can still be 

 perceived, and if a section be made of it, all the characters of the mam- 

 mary gland can be made out in its interior. 



In diffused gangrene, however, the glandular tissue is deep-red in 

 color, softened, and filled with pulpy cavities ; the ducts and sinuses are 

 filled or choked with coagulated milk, pus and serum, the whole .forming 

 a diversely-colored fluid. In the veins are sometimes blood-clots, varia- 

 ble in color and consistence ; gas and foetid fluids escape from the tissue 

 on section '; and the oedema is found to be due to infiltrations of yellow 

 serum in which are brown and greenish streaks. This fluid, examined 

 microscopically, has much the appearance of that found in animals which 

 have died from septikaemia. Shreds of necrotic tissue are also met with. 



Causes. 



Mammitis appears to be due to the most diverse causes. Among the 

 principal predisposing causes, the first is lactation — the disease appear- 

 ing immediately before or soon after parturition ; and those animals 

 whose mammae are most active at this period, are those most frequently 

 attacked. In the great majority of cases in the Cow — in which animal it 

 is most serious — it follows within a month after parturition. It is true 

 that, in certain maladies — as foot-and-mouth disease, cow-pox, sheep-pox, 

 etc. — the udder may be affected at any time ; yet the lactation period, 



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