menstrual period which has been accompanied by ovulation.

[97] Robinson, _American Gynecological and Obstetrical Journal_, August,
1905.

[98] Bossi, _Annali di Ostetrica e Ginecologia_, September, 1896;
summarized in the _British Medical Journal_, October 31, 1896. As regards
the more normal influence of the ovaries over the uterus, see e.g.
Carmichael and F.H.A. Marshall, "Correlation of the Ovarian and Uterine
Functions," _Proceedings Royal Society_, vol. 79, Series B, 1907.

[99] Beuttner, _Centralblatt fuer Gynaekologie_, No. 49, 1893; summarized in
_British Medical Journal_, December, 1893. Many cases show that pregnancy
may occur in the absence of menstruation. See, e.g., _Nouvelles Archives
d'Obstetrique et de Gynecologie_, 25 Janvier, 1894, supplement, p. 9.

[100] It is still possible, and even probable, that the primordial cause
of both phenomena is the same. Heape (_Transactions Obstetrical Society of
London_, 1898, vol. xl, p. 161) argues that both menstruation and
ovulation are closely connected with and influenced by congestion, and
that in the primitive condition they are largely due to the same cause.
This primary cause he is inclined to regard as a ferment, due to a change
in the constitution of the blood brought about by climatic influences and
food, which he proposes to call gonadin. (W. Heape, _Proceedings of Royal
Society_, 1905, vol. B. 76, p. 266.) Marshall, who has found that in the
ferret and other animals, ovulation may be dependent upon copulation, also
considers that ovulation and menstruation, though connected and able to
react on each other, may both be dependent upon a common cause; he finds
that in bitches and rats heat can be produced by injection of extract from
ovaries in the oestrous state (F.H.A. Marshall, _Philosophical
Transactions_, 1903, vol. B. 196; also Marshall and Jolly, id., 1905, B.
198). Cf. C.J. Bond, "An Inquiry Into Some Points in Uterine and Ovarian
Physiology and Pathology in Rabbits," _British Medical Journal_, July 21,
1906.

[101] Pouchet, _Theorie de l'Ovulation Spontanee_, 1847. As Blair Bell and
Pontland Hick remark ("Menstruation," _British Medical Journal_, March 6,
1909), the repeated oestrus of unimpregnated animals (once a fortnight in
rabbits) is surely comparable to menstruation.

[102] Tait, _Provincial Medical Journal_, May, 1891; J. Beard, _The Span
of Gestation_, 1897, p. 69. Lawson Tait is reduced to the assertion that
ovulation and menstruati