230 BREEDING 



In order that an impregnated ovum may proceed to develop into a. 

 foetus, the womb with which it must establish a connection will require to- 

 be in a healthy condition. Many mares fail to breed, not from any 

 structural defect of the reproductive organs, but from a functional derange- 

 ment of the mucous membrane of the uterus or vagina, whose vitiated 

 secretion imperils, if it does not immediately destroy, the life of the sperma- 

 tozoa, or should they escape and impregnation take place, the fertilized 

 ovum sooner or later succumbs to its unhealthy environment. Many of 

 those cases where mares return to the horse and receive service again and 

 again without proving fruitful, result from some one or other abnormal 

 state of the uterus unfitting it to nurture the impregnated germ. 



Although little can be done to rectify those graver structural defects of 

 the ovaries and the uterus which add to the prevalence of sterility, much 

 may be done to prevent that greater .waste resulting from obstructive 

 conditions affecting the mouth and neck of the womb, which prevent the 

 semen from entering it. 



It has repeatedly been affirmed and implied that in the act of coition 

 the spermatic fluid of the horse is deposited in the vagina of the mare, and 

 that the spermatozoa subsequently enter the uterus by virtue of their own 

 powers of movement or are sucked into the latter organ during its relaxa- 

 tion, when copulation is completed. While allowing the operation of both 

 these forces in the act of insemination, it is impossible to disregard the 

 mutual adaptation of the male and female organs to the purpose of convey- 

 ing the semen directly into the mouth of the womb. The projection of the 

 urethral canal beyond the glans penis in a state of erection would seem to 

 indicate that this arrangement was designed to ensure the delivery of the 

 male element into the mouth of the uterus. 



That this should take place is not absolutely necessary to fertilization. 

 It has been proved by experiment that the injection of semen into the 

 vagina alone may be sufficient to induce pregnancy. Because this is so, it 

 has been argued that the spermatic fluid in the act of copulation in the 

 horse is not discharged into the uterus. It seems to the writer that such 

 a conclusion is not warranted by the facts. 



That the introduction of semen into the vagina is followed by preg- 

 nancy does not exclude the possibility of its being deposited directly into 

 the mouth of the womb during the act of coition, but would rather appear 

 to afford a supplementary provision for impregnation in the event of this- 

 not being effected. 



Whether insemination is brought about by one method or the other, or 

 both, a clear entrance to the uterus is an indispensable condition to- 

 impregnation by natural means. 



