196 The Diseases of Animals 
which is an abnormal sexual excitement. The animal 
being in heat very frequently, or continuously, will 
take service by a bull, but will rarely become preg- 
nant. Unless the cause of the sexual excitement can 
be located and removed (which is seldom), the best 
treatment is to spay the animal and fatten her for the 
market. 
Nervous, vicious animals are not so likely to breed 
as those of a milder temperament. Aged animals, 
especially mares, that have not been bred for some 
time, are extremely difficult to impregnate. This is 
well illustrated by the difficulty experienced in breed- 
ing mares that have been used for racing until they 
are ten or twelve years old, and are then retired for 
breeding purposes. A large percentage of them fail 
to become pregnant. Mares that have been bred 
frequently often will continue to breed after they- are 
twenty years of age. Fat animals are seldom good 
breeders, and it is often difficult to impregnate them. 
Animals intended for breeding should be in very 
moderate flesh. Active exercise, just before the ani- 
mal is bred, is conducive to fertilization. 
In the large animals, such as the mare and the cow, 
it is usually an excellent plan, when there is difficulty 
in getting them to breed, to ‘open the womb.” This 
is done by inserting the oiled hand and arm into the 
vagina, finding the opening into the womb, and grad- 
ually dilating it by inserting one or more fingers, 
until the passage is considerably enlarged. A sponge 
tent can also be inserted, which absorbs moisture, 
swells, and automatically dilates the passage. In some 
