Acute Mammitis 951 



of the cases. In our experience resolution has been very rare 

 indeed. 



Too frequently the acute disease passes into the chronic form. 

 If the changes brought about by the disease are not too serious, 

 the period of rest, while the cow is dry, may afford an oppor- 

 tunity for the complete resolution of the gland, so that when she 

 again calves she may yield almost or wholly her normal amount 

 and quality of milk. If the gland has been once seriously 

 affected, it is rendered so vulnerable to any subsequent infection 

 that the disease may at any time recur. 



b. Suppuration and the formation of abscesses may originate 

 in any of the tissues of the gland — in the subcutaneous connec- 

 tive tissue, the inter-lobular connective tissues, or the paren- 

 chyma of the gland. 



In many cases we observe that the suppuration affects chieflj' 

 the epithelium of the milk canals and acini, to constitute ca- 

 tarrhal mastitis, in which case there may not be very extensive 

 swelling, and the area of the disease may be more or less con- 

 fined to the milk cistern and the larger milk canals, without in- 

 volving seriously the acini themselves. Rarely an abscess 

 forms in the milk cistern, without involving the parenchyma 

 of the gland at all. Abscesses in the milk cistern are very liable 

 to cause the destruction of the milk canals, by causing their com- 

 plete atresia, so that they can never re-open. The formation of 

 ' abscesses in the udder leads almost uniformly to the permanent 

 destruction of the involved quarter, though in rare instances 

 there may be a partial restoration of milk production after the 

 next calving. 



Purulent mastitis may lead, in somewhat . rare instances, to 

 pyaemia or to metastatic complications of the joints or tendon 

 sheaths. Abscesses may become encapsulated, with indurated 

 abscess walls which surround the pus, and continue as hard 

 swellings in the affected part. 



c. Atrophy of the gland substance occurs frequently, with or 

 without induration. 



Following many cases of acute mastitis, a chronic inflamma- 

 tion remains, which causes, in addition to the atrophy of the 

 substance of the gland itself, an extensive hyperplasia of the 

 inter-lobular substance. The gland becomes indurated, hard, 

 and incapable of secreting milk. The indurated gland may as- 



