188 DISEASES OP THE HOKSE. 



position and presentation has been rendered natural, traction on 

 the fetus must be made only during a labor pain. If a mare is 

 inclined to kick, it may be necessary to apply hobbles to protect the 

 operator. 



Difficult paetueitiokt teom narrow pelvis. — ^A disproportion 

 between the fetus got by a large stallion and the pelvis of a small 

 dam is a serious obstacle to parturition, sometimes seen in the mare. 

 This is not the rule, however, as th« foal up to birth usually accommo- 

 dates itself to the size of the dam, as illustrated in the successful 

 crossing of Percheron stallions on mustang mares. If the dispro- 

 portion is too great the only resort is embryotomy. 



Fracttjeed hip bones. — More commonly the obstruction comes 

 from distortion and narrowing of the pelvis as the result of fractures. 

 (Plate XIII, fig. 2.) Fractures at any point of the lateral wall or 

 floor of the pelvis are repaired with the formation of an extensive 

 bony deposit bulging into the passage of the pelvis. The displace- 

 ment of the ends of the broken bone is another cause of constriction, 

 and between the two conditions the passage of the fetus may be ren- 

 dered impossible without embryotomy. Fracture of the sacrum (the 

 continuation of the backbone forming the croup) leads to the de- 

 pression of the posterior part of that bone in the roof of the pelvis 

 and the narrowing of the passage from above downward by a bony 

 ridge presenting its sharp edge forward. 



In all cases in which there has been injury to the bones of the pelvis 

 the obvious precaution is to withhold the mare from breeding and to 

 use her for work only. 



If a mare with a pelvis thus narrowed has got in foal inadvert- 

 ently, abortion may be induced in the early months of gestation by 

 slowly introducing the oiled finger through the neck of the womb 

 and following this by the other fingers until the whole hand has 

 been introduced. Then the water bags may be broken, and with the 

 escape of the liquid the womb will contract on the solid 'fetus and 

 labor pains will ensue. The fetus being small will pass easily. 



Tumors in tub vagina and pelvis.— Tumors of various kinds may 

 form in the vagina or elsewhere within the pelvis, and when large 

 enough will obstruct or prevent the passage of the fetus. Gray mares, 

 which are so subject to black pigment tumors (melanosis) on the 

 tail, anus, and vulva, are the most liable to suffer from this. Still 

 more rarely the wall of the vagina becomes relaxed, and being pressed 

 by a mass of intestines will protrude through the lips of the vulva 

 as a hernial sac, containing a part of the bowels. If a tumor is small 

 it may only retard and not absolutely prevent parturition. A hernial 

 protrusion of the wall of the vagina may be pressed back and 

 emptied, so that the body of the fetus engaging in the passage may 



