574 OVULATION AND FUNCTION OF MENSTRUATION. 



Accidental causes, however, sometimes disturb this regular course 

 or passage of the egg. The egg may be arrested, for example, 

 at the surface of the ovary, and so fail to enter the tube at all. 

 If fecundated in this situation, it will then give rise to " ovarian 

 pregnancy." It may escape from the fimbriated extremity into the 

 peritoneal cavity, and form attachments to some one of the neigh- 

 boring organs, causing "abdominal pregnancy;" or finally, it may 

 stop at any part of the Fallopian tube, and so give origin to " tubal 

 pregnancy." 



The egg, immediately upon its discharge from the ovary, is ready 

 for impregnation. If sexual intercourse happen to take place about 

 that time, the egg and the spermatic fluid meet in some part of the 

 female generative passages, and fecundation is accomplished. It 

 appears from various observations of Bischoff, Coste, and others, 

 that this contact may take place between the egg and the sperm, 

 either in the uterus or any part of the Fallopian tubes, or even 

 upon the surface of the ovary. If, on the other hand, coitus do not 

 take place, the egg passes down to the uterus unimpreguated, loses 

 its vitality after a short time, and is finally carried away with the 

 uterine secretions. 



It is easily understood, therefore, why sexual intercourse should 

 be more liable to be followed by pregnancy when it occurs about 

 the menstrual epoch than at other times. This fact, which was long 

 since established as a matter of observation by practical obstetri- 

 cians, depends simply upon the coincidence in time between men- 

 struation and the discharge of the egg. Before its discharge, the 

 egg is immature, and unprepared for impregnation ; and after the 

 menstrual period has passed, it gradually loses its freshness and 

 vitality. The exact length of time, however, preceding and follow- 

 ing the menses, during which impregnation is still possible, has not 

 been ascertained. The spermatic fluid, on the one hand, retains its 

 vitality for an unknown period after coition, and the egg for an 

 unknown period after its discharge. Both these occurrences may, 

 therefore, either precede or follow each other within certain limits, 

 and impregnation be still possible ; but the precise extent of these 

 limits is still uncertain, and is probably more or less variable in 

 different individuals. 



The above facts indicate also the true explanation of certain 

 exceptional cases, which have sometimes been observed, in which 

 fertility exists without menstruation. Various authors (Churchill, 

 Reid, Velpeau, &c.) have related instances of fruitful women in whom 



