MENSTRUATION. 711 



to the observations of Bischoff, Pouchet, and Raciborski, the regular 

 time for this rupture and discharge is not at the commencement, but 

 toward the termination of the period. According to those of Coste, 1 

 the follicle ruptures sometimes in the early part of the menstrual epoch, 

 sometimes later. So far as we can learn, therefore, the precise period 

 is not invariable. Like the menses themselves, it may take place a 

 little earlier, or a little later, according to circumstances ; but it always 

 occurs in connection with the menstrual flow, and constitutes the essen- 

 tial part of the catamenial process. 



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 is different, in quadrupeds and the human species, 

 and in birds and reptiles. In the latter, the bulk of the egg or eggs is 

 so great as to fill or even to distend the cavity of the oviduct ; and the 

 mass is accordingly embraced by the muscular wall of the canal and 

 carried downward by its peristaltic action. In the mammalians, 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 epithe- 

 lium; and the movement of the cilia, which is from the ovary toward 

 the uterus, produces a kind of vortex, by which the egg is drawn toward 

 the narrow portion of the tube, and thence conducted to the cavity of 

 the uterus. 



Accidental causes may sometimes disturb the regular course of 

 passage of the egg. It may be arrested at the surface of the ovary, 

 and thus fail to enter the tube at all. If it be fecundated and go on to 

 partial development in this situation, it will give rise to " ovarian 

 pregnancy." The egg 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 so give origin to u tubal 

 pregnancy." 



The egg, immediately upon 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 generative 

 passages, and fecundation is accomplished. It appears from the obser- 

 vations of Bischoff, Coste, and Martin Barry 2 upon rabbits, that the 

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

 the uterus or any part of the Fallopian tubes, or even upon the surface 

 of the ovary. If, on the other hand, sexual coitus do not take place, 

 the egg passes down to the uterus unimpregnated, loses its vitality after 

 a short time, and is carried away with the uterine secretions. 



It is easily understood, therefore, why sexual intercourse should be 

 more liable to be followed by pregnancy when occurring about the 



1 Histoire du DSveloppement des Corps Organises. Paris, 1847, tome i. p. 221. 

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



