The Brood Mare 281 
containing the spermatozoa into the vagina of the mare, 
from whence the spermatozoa pass into the uterus and 
from there into the Fallopian tube where they meet the 
ovum or female cells and impregnation proper takes place. 
This may not occur for several hours after copulation. 
The mare produces one, and sometimes more than one 
ovum during the period of heat, while the semen ejected 
by the horse contains hundreds of the microscopic sperm- 
cells, and only one of which may unite with the ovum to 
produce the colt. Thus the horse at each act of copula- 
tion produces many more spermatozoa than are actually 
needed, provided of course that he is a normal, healthy 
horse. The idea in artificial impregnation is to collect 
some of these spermatozoa which are not needed by the 
mare bred, and transfer them to other mares. If prop- 
erly conducted this will produce exactly the same im- 
pregnation as if the mares were bred directly by the stal- 
lion. 
The breeding bag is a rubber bag which is tied on to the 
end of the penis. When the penis is withdrawn after 
service, the bag with the ejected semen comes back with 
it. The bag is then placed in warm water, 95° to 101° 
temperature. A syringe is filled with the fluid, and emp- 
tied into the vagina of the mare. As only a part of the 
fluid is used for one impregnation, a number of mares 
may be bred from this one bag of semen. The objections 
to this method are: stallions may refuse to serve with the 
breeding bag attached; the fluid may become contam- 
inated with germs; the fluid may be exposed to the 
light and the sperm-cells killed; and lastly, the stallion, 
even though it may not refuse at first, usually does refuse 
to serve properly after the breeding bag has been used 
for some time, 
