606 REPRODUCTION. 



the termination of the period. According to Coste,* it is sometimes 

 earlier, sometimes later. So far as we can determine, its precise period 

 is not invariable. Like the menses themselves, it may be hastened or 

 retarded according to circumstances ; but it always occurs in connec- 

 tion with the menstrual flow, and constitutes the most important part 

 of the process in regard to reproduction. 



The egg, when discharged from the ovary, enters the fimbriated 

 extremity of the Fallopian tube, and commences its passage toward 

 the uterus. The mechanism by which it finds its way into and through 

 the Fallopian tube in quadrupeds and man is different from that in 

 birds and reptiles. In the latter, the bulk of the eggs is sufficient to 

 distend the oviduct ; and the mass, embraced by the muscular wall 

 of the canal, is carried downward by peristaltic action. In mamma- 

 lians, on the other hand, the egg is microscopic in size. The wide 

 extremity of the Fallopian tube, directed toward the ovary, is lined 

 with ciliated epithelium ; and the movement of the cilia, which is from 

 the ovary toward the uterus, produces a kind of vortex, by which the 

 egg is conducted into the narrow portion of the tube, and thence down- 

 ward to the uterus. 



Accidental causes may sometimes disturb the passage of the egg. 

 It may be arrested at the surface of the ovary, and thus fail to enter 

 the Fallopian tube. If it be fecundated and go on to partial develop- 

 ment in this situation, it gives rise to "ovarian pregnancy." It may 

 escape from the fimbriated extremity of the Fallopian tube into the 

 peritoneal cavity, and form attachments to a neighboring organ, causing 

 " abdominal pregnancy ;" or finally it may stop in some part of the 

 Fallopian tube, and thus give origin to " tubal pregnancy." 



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

 for impregnation. If sexual intercourse take place about that time, 

 the egg and the spermatozoa meet in some part of the female genera- 

 tive passages, and fecundation is accomplished. It appears from the 

 observations of Bischoff, Coste, and Barry)" upon rabbits, that the 

 contact of the egg and the spermatozoa may take place either in the 

 uterus or the Fallopian tubes, or on the surface of the ovary. If, on 

 the other hand, there be no sexual coitus, the egg passes the Fallopian 

 tube unimpregnated, loses its vitality after a time, and is carried away 

 with the uterine secretions. 



For this reason sexual intercourse is most liable to be followed by 

 pregnancy when occurring at or soon after the menstrual epoch. 

 Before its discharge, the egg is immature and unfit for impregnation ; 

 and some days afterward, it loses its freshness and vitality. The exact 

 length of time, preceding and following the menses, during which im- 

 pregnation is possible, has not been ascertained. The spermatozoa, 

 on the one hand, retain their vitality for an unknown period after 

 coition, and the egg for an unknown period after its' discharge. These 



* Histoire du Developpment des Corps Organises. Paris, 1847, tome i., p. 221. 

 f Philosophical Transactions. London, 1839, p. 315. 



