DISEASES OP THE GENERATIVE OEGANS. 167 



seen in the mare. This is not the rule, however, as the foal up to 

 birth usually accommodates itself to the size of the dam, as illustrated 

 in the successful crossing of Percheron stallions on mustang mares. 

 If the disproportion is too great the only resort is embryotomy. 



FBACTUEED HIP BONES. 



More commonly the obstruction comes from distortion and narrow- 

 ing of the pelvis as the result of fractures. (Plate XV, 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 displacement of the ends of the 

 broken bone is another cause of constriction, and between the two con- 

 ditions the passage of the fetus may be rendered impossible without 

 embryotomy. Fracture of the sacrum (the continuation of the back- 

 bone forming the croup) leads to the depression of the posterior part 

 of that bone in the roof of the pelvis and the narrowing of the pas- 

 sage 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 inadvertently, 

 abortion may be induced in the early months of gestation by slowly 

 introducing the oiled finger through the neck of the womb and fol- 

 lowing this by the other fingers until the whole hand has been intro- 

 duced. 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 THE 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 pig- 

 ment tumors (melanosis) on the tail, anus, and vulva, are the most 

 likely to suffer from this. Still more rarely the wall of the vagina 

 becomes relaxed, and being pressed by a mass of intestines will pro- 

 trude through the lips of the vulva as a hernial sac, containing a part 

 of the bowels. Where 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 find no further obstacle. When 

 a tumor is too large to allow delivery the only resort is to remove it, 

 but before proceeding it must be clearly made out that the obstruc- 

 tion is a mass of diseased tissue, and not a sac containing intestines. 



