256 Veterinary Obstetrics 



Others maintain that, during copulation, the meatus urinarius 

 of the male penis is pressed against the os uteri externum of the 

 female at the moment of ejaculation and that the semen is in- 

 jected directly into the uterus through the cervical canal, 

 lyittle evidence exists in favor of such assumption and much 

 against it. In the mare, it is especially notable that large 

 quantities of semen are expelled from the vulva immediately 

 after the completion of copulation, which would signify that it 

 had probably not passed beyond the vagina. If the vaginal 

 cavity is examined immediately after copulation, large quantities 

 of semen will be found in it, apparently the normal volume dis- 

 charged at a single copulation. If this is largely expelled from 

 the vagina immediately after ejaculation, it would scarcely 

 appear that it was first thrown into the uterine cavity or cervical 

 canal, but that it was discharged against the anterior wall of the 

 vagina, especially the os uteri externum, and that only a very 

 small proportion of the fecundating cells pass beyond the vagina 

 to assume any important part in the process of fertilization. 

 Some of the spermatozoa pass through the cervical canal, uterine 

 and cornual cavities, reach the oviduct and meet the ovum or 

 ova, where one male cell serves to fecundate each female cell or 

 ovum, while the other spermatozoa perish. Most of the sperm- 

 atozoa are expelled from the vagina immediately after copulation. 



Occlusion of the os uteri, as a fundamental cause of sterility, con- 

 sists of such complete atresia, or closure, of the cervicdl canal as to 

 render the passage of the microscopic spematozoa improbable or im- 

 possible. In the oviduct with a canal admitting a large horsehair, 

 the size of the channel is abundant for purposes of fecundation and, 

 so far as we can determ.ine, a like opening through the cervical 

 canal fulfills all demands for impregnation. 



According to this view, the smallest recognizable opening 

 through the os uteri and cervical carfal constitutes a reproduc- 

 tively 7iormal condition and, ere we can diagnose occlusion of the 

 OS, we need to determine that the passage of microscopic sperma- 

 tozoa, endowed with vigorous motile power and in their normal 

 element, is impracticable. Hence, in our judgement, if the 

 smallest sound, possessing adequate rigidity to render its insertion 

 practicable, can be passed through the cervical canal without 

 undue force, the diagnosis of occlusion of the os uteri is not 

 warranted. 



