172 DISEASES OF THE HORSE. 
CASTRATION BY THE COVERED OPERATION. 
This is only required in case of hernia or protrusion of bowels or 
omentum into the sac of the scrotum, and consists in the return of 
the hernia and the application of the caustic clamps over the cord 
and inner walls of the inguinal canal, so that the walls of the latter 
become adherent above the clamps, the canal is obliterated, and fur- 
ther protrusion is hindered. For the full description of this and of 
the operation for hernia for geldings, see remarks on hernia. 
CASTRATION OF THE MARE. 
Castration is a much more dangerous operation in the mare than in 
the females of other domesticated quadrupeds and should never be 
resorted to except in animals that become unmanageable on the recur- 
rence of heat and that will not breed or that are utterly unsuited to 
breeding. Formerly the operation was extensively practiced in 
Europe, the incision being made through the flank, and a large pro- 
portion of the subjects perished. By operating through the vagina 
the risk can be largely obviated, as the danger of unhealthy inflam- 
mation in the wound is greatly lessened. The animal should be 
fixed in a trevis, with each foot fixed to a post and a sling placed 
under the body, or it may be thrown and put under chloroform. 
The manual operation demands special professional knowledge and 
skill, but it consists essentially in making an opening through the 
roof of the vagina just above the neck of the womb, then following 
with the hand each horn of the womb until the ovary on that side 
is reached and grasped between the lips of forceps and twisted off. 
It might be torn off by an écraseur especially constructed for the 
purpose. The straining that follows the operation may be checked 
by ounce doses of laudanum, and any risk of protrusion of the bowels 
may be obviated by applying the truss advised to prevent eversion 
of the womb. To further prevent the pressure of the abdominal con- 
tents against the vaginal wound the mare should be tied short and 
high for twenty-four or forty-eight hours, after which I have found 
it best to remove the truss and allow the privilege of lying down. 
Another important point is to give bran mashes and other laxative 
diet only, and in moderate quantity, for a fortnight, and to unload 
the rectum by copious injections of warm water in case impaction is 
imminent. 
STERILITY. 
Sterility may be in the male or in the female. If due to the stal- 
lion, then all the mares put to him remain barren; if the fault is in 
the mare, she alone fails to conceive, while other mares served by the 
same stallion get in foal. 
In the stallion sterility may be due to the following causes: (a) 
Imperfect development of the testicles, as in cases in which they are 
