PASSAGE OF OVA INTO THE FALLOPIAN TUBES 779 



ing a plexus of blood-vessels, upon the surface of the ovary. At its most 

 prominent portion, is an ovoid spot in which the membranes are entirely free 

 from blood-vessels. At this spot, which is called the macula folliculi, the 

 coverings finally give way and the contents of the follicle are discharged. 

 For a short time anterior to the rupture of the follicle, important changes 

 have been going on in its structure. In the first place, the non-vascular por- 

 tion situated at the very surface of the ovary undergoes fatty degeneration, 

 by which this part of the wall gradually becomes weakened. At the same 

 time, at the other portions of the follicle, there is a proliferation of cells 

 which project into the interior, and an extension, into the interior, of blood- 

 vessels in the form of loops. These changes, with an increase. in the pressure 

 of liquid and the fatty degeneration of the macula, cause the follicle to burst ; 

 and with the liquid, the discus proligerus and the ovum are expelled. The 

 formation of a cell-growth in the interior of the follicle is the beginning of 

 the corpus luteum ; and this occurs some time before the discharge of the 

 ovum takes place. 



The time at which the follicle ruptures, particularly with reference to the 

 menstrual period, is not definite ; but it is certain that while sexual excite- 

 ment probably hastens the discharge of an ovum by producing a greater or 

 less tendency to congestion of the internal organs, ovulation takes place in- 

 dependently of the action of coition. The opportunities for determining 

 this fact in the human female are not frequent ; but it has been fully dem- 

 onstrated by observations upon the inferior animals, and there is now no 

 doubt with regard to the -identity of the phenomena of rut and of menstru- 

 ation. At stated periods marked by the phenomena of menstruation, one 

 Graafian follicle and sometimes more than one becomes distended and 

 usually ruptures and discharges its contents into the Fallopian tubes. This 

 discharge of an ovum or ova may occur at the beginning, at the end, or at 

 any time during the continuance of the menstrual flow. Upon this point the 

 observations of Coste seem entirely conclusive. In a woman who died on the 

 first day of menstruation, he found a recently ruptured follicle ; in other in- 

 stances, at a more advanced period and toward the decline of the menstrual 

 flow, he found evidences that the rupture had occurred later ; in the case of 

 a female who drowned herself four or five days after the cessation of the 

 menses, a follicle was found in the right ovary, so distended that it was rupt- 

 ured by very slight pressure ; and other instances were observed in which 

 follicles were not ruptured during the menstrual period. 



PASSAGE OF OVA IXTO THE FALLOPIAN TUBES. 



The fact that the ova in the great majority of instances pass into the 

 Fallopian tubes is sufficiently evident. The fact, also, that ova may fall into 

 the cavity of the peritoneum is illustrated by the occasional occurrence of 

 extraiiterine pregnancy, a rare accident, which shows that in all probability 

 the failure of unimpregnated ova to enter the tubes is exceptional. As regards 

 the mechanism of the passage of the ova into the tubes, however, the expla- 

 nation is difficult. At the present time there are two theories with regard 



