CHAPTER III 

 MASTITIS CAUSED BY EXTERNAL FORCE 

 This mastitis may be divided into injuries and wounds. 



INJURIES OF THE UDDER 



An injury of the udder is a destruction of the udder 

 tissues through a more or less uninjured skin covering. 



Causes. — Injuries of the udder may be produced by a 

 blow, by squeezing or by being trod upon. 



One must discriminate between the primary effect, 

 that is the primary lesion produced by the direct effect of 

 the external force, and the subsequent inflammation. 



Primary Lesion. — The force can produce an imme- 

 diate necrosis of the softer cells, especially the epithelial 

 cells, in a circumscribed area and rupture of blood- and 

 lymph-vessels with an extravasation of blood and lymph 

 into the intralobular connective tissue particularly. This 

 hemorrhage can also get into the milk passages and give 

 rise to bloody milk. As a rule the hemorrhage soon stops. 

 As the tissue becomes distended with blood and lymph the 

 pressure becomes so great that fui'ther hemorrhage is 

 mechanically lessened or prevented. Furthermore the 

 destroyed cells liberate fibrin ferment which aids in coagula- 

 tion of the blood, thus preventing fm-ther hemorrhage. 

 Should the force strike an exposed part which already 

 shows a blood infiltration, a progressive necrosis of the 

 rather poorly nourished cells can easily take place. Seldom 

 is the udder tissue alone affected, as usually the skin is in- 

 volved at the same time and manifests superficial abrasions 

 of the epidermis and swelling and blood infiltration of the 

 corium and subcutaneous connective tissue. 



These alterations in the udder tissue then call forth 

 an inflammation with emigration of leucocytes. This in- 



