CIRCULATORY DISTURBANCES 89 



return flow of the blood — that is, venous stasis — but is due to 

 an active hyperemia. This hyperemia, characterized by its 

 redness, swelling, heat and increased sensibility, extends 

 beyond the vagina. 



The swelling of the udder and surroundings must be 

 attributed to the same causes. But it happens that this 

 so-called oedema increases to an extent sufficient to worry the 

 owner. The oedema extends at times backwards and up to the 

 vulva ; the perineal region is swollen, its skin tight, the vulva 

 enlarged and the skin of the labire glistening. 



The udder has reached such dimensions that the skin is 

 tense and the teats barely project beyond the swollen udder; 

 in other cases the teats are full and milk runs from them. 

 All these phenomena only put iu their appearance at the end 

 of pregnancy, and become fully developed only a few days 

 before parturition. 



The swelling may extend along the umbilicus up to the 

 fore legs. In primipara? this oedema occasionally becomes so 

 prominent, that the inferior abdominal wall hangs down like a 

 pillow from the udder to the dewlap. Such an extensive 

 tumefaction probably depends also on a disturbed circulation 

 — that is, venous stasis. 



The blood of the udder of the cow returns by two 

 channels. One part returns through the external mammary 

 vein, while the balance flows off through a branch of the 

 external pubic vein, which runs upwards from the posterior 

 quarter into the obturator and internal pubic vein. 



The venous blood carried off in the above named manner 

 therefore has not favorable conditions for its course ; conse- 

 quently the slightest disturbance may retard the return flow. 



On account of the swelling of the vulva and the increased 

 amount of blood at the vagina, a considerable accumulation of 

 blood also takes place in the venous network of the vagina ; 

 this venous network also empties into the internal pubic vein. 

 In consequence of the stasis experienced by the blood of 

 the ascending branch of the external pubic vein, a passive 

 hyperemia takes place iu its tributaries. 



