446 HAYATO ARAI 
In the case of the human female there are several opinions as 
to the usual time for the discharging of the ovum. Some authors 
report that ovulation occurs before menstruation; others, during 
that process, and still others, that it follows menstruation. 
Hergesell (’05) holds that ovulation precedes menstruation for 
the reason that the most usual period for ovulation in the human 
female, as in many of the lower mammals, was during a definitive 
oestrus following the preoestrus; for the period of most active 
sexual feeling is generally just after the close of the menstrual 
period, while, according to Raciborsky (Traité de Menstruation: 
cited from ‘‘Physiology of reproduction, Marshall,’ ’10), this 
is also the commonest season for fertile coition. Contrary to 
this, Bryce and Teacher (’08) hold that the ovum is discharged 
shortly after the cessation of the last menstruation. 
Touching the question whether a special stimulus induces 
ovulation in woman, Oliver (’02) regards the view that coitus 
accelerates ovulation as the more probable, since at this time 
there is an increased blood supply to the whole genital tract. 
Heape (’05), however, maintains that the cause which deter- 
mines the rupture of the Graafian follicle is, in the rabbit, the 
stimulation of erectile tissue, due to a nervous reflex, and not 
simply the result of internal pressure arising from an increased 
blood supply or a greater quantity of liquor folliculi. 
Harper (’04), in pigeons, concludes that ovulation requires 
only a slight stimulus, ‘mental,’ and that the presence of sperm 
in the oviduct cannot be regarded as important. Ko6lliker (’02) 
considers the cause of rupture as a simple mechanical process 
because the irritation of vasomotor nerves increases the pressure 
of the liquor folliculi thus inducing the rupture. 
From the foregoing. it is evident that the real cause of the rup- 
ture of the Graafian follicle is not clearly established, and there- 
fore that the factors which may induce ovulation require further 
study. 
Whatever may be the final conclusion as to the cause, it is 
clear that ovulation is closely related to the maturing of the ovary, 
as my present study indicates. 
