20 MASTITIS OF THE COW 



These factors adequately support each other, that is, a 

 locahzed primary lesion is caused by an organism of low 

 virulence and slow growth, while, on the other hand, 

 the diffuse primary lesion is caused by an organism 

 of high virulence and rapid growth. When the viru- 

 lence is extremely high inflammation may be retarded or 

 prevented. 



Quality. — The alterations in the primary lesion are of 



a retrogressive type, and are usually of degenerative or 



necrotic character. These retrogressive 



changes, however, may vary in degree. 



In the mildest cases they may consist 



only of degeneration of the epithelium. 



The epithelium may however become 



necrotic and a croupous membrane form. 



o 1..-U • r .• If the connective tissue becomes necrotic 



Fia. 3. — Milk - infection 



Khy&^S "^"slvire ^ dccp diphthcrltic membrane is pro- 

 I'l^iviMi "''^Idif'iT. duced. Greater portions of the udder 

 dSt'nL7or8*.^'hf^?r?- may become necrotic, as the single tu- 



lobular connective tissue iaii /»ii iiir» 



distended with red blood bulcs. Or gTOups 01 tlicsc tuDulcs, lomi- 



cells following hemorrhage. . , , . ._,, 



The tubules are compressed mff noQular uccrosis. ihc cutirc Dart 



and contain desquamated ,,, ■,, <tp , 'ni 



epithelial cells. Numeroua qi tlic uddcr aficcted Hiav raoidlv be- 



staphylococoi were demon- .' ir ^ 



S^'baiteriaf staff ^^ ^^ couic uccrotic or dcvclop iuto dlffusc 

 gangrene (Fig. 3). 



The quantity and quality of the primary lesion depend 

 upon the character of the infectious organism and the con- 

 dition of the udder. The more virulent the organism, the 

 greater is the area and the more severe the character of the 

 primary lesion. 



Organisms of the same virulence however produce a 

 greater primary lesion after parturition than during the 

 gestation period. Under identical conditions, that is, the 

 same virulence of organisms and same time after parturi- 

 tion, the primary lesion is greater in good milch cows than 

 in those that are poor milkers. These circumstances are 



