30 



MASTITIS OF THE COW 



and usually is not circumscribed by an inflammation. The 

 necrosis develops slowly at its periphery through necrosis 

 of the cell wall. This cell wall around the spreading area 

 of necrosis, however, is maintained by proliferation of new 

 connective-tissue cells. In this manner the nodules develop 

 and become the size of hemp seed or larger. 



Following this development of the lesions many adja- 

 cent areas of necrosis may coalesce and finally produce 

 great necrotic nodules the size of a hen's egg. 



The infectious organisms may be picked up by the 

 leucocytes and carried into the lymph 

 spaces of the stroma inducing the for- 

 mation of the new areas of necrosis or 

 daughter nodules. 



The necrotic nodules may open a 

 milk-duct and thus induce a secondary 

 milk-infection [parenchymatous mas- 

 titis]. In the same way, but less fre- 

 quently, they may open the skin by 

 ulceration and cause fistulse. 



Because of their position in the stro- 

 ma the nodules compress the tubules 

 and produce pressure atrophy of their 

 cells. The milk is most altered in quan- 

 tity which is decreased more or less. The composition is 

 less changed. The fat content lessened. It is poor milk. 

 Complication by saprophytic invasion is rendered im- 

 possible. It is closed off by a completely circumscribing 

 wall of connective-tissue cells. 



If a secondary milk-infection is produced by ulceration 

 of a milk-duct or a fistula formed by ulceration of the skin, 

 saprophytic invasion with its subsequent putrid softening 

 is possible through the openings in the necrotic areas in 

 the stroma. 



Fia. 5. — Stroma-infec- 

 tion [interstitial mastitis] 

 of chronic character. Pyo- 

 bacillosia (150). Two 

 groups of cells (emigration) 

 are visible in the swollen 

 cellular intralobular con- 

 nective tissue. The tu- 

 bules are compressed. In 

 one tubule a few cells are 

 present. By the use of 

 bacterial stains a few bac- 

 teria, pyogenes bacilli, were 

 demonstrated in the centre 

 of the cellular foci. 



