FORMATION OF THE CORPUS LUTEUM. 895 







it is well known that, although pregnancy seldom recurs during the contin- 

 uance of lactation, the rule is by no means invariable. 



74.'>. The function of the Female, during the coitus, is essentially passive. 

 When the sexual feeling is strongly excited, there is a considerable degree 

 of turgesceuce in the erectile tissue surrounding the vagina, and composing 

 the greater part of the nymphse and the clitoris; and there is an increased 

 secretion from various glandular follicles. 1 But these changes are by no 

 means necessary for effectual coition ; since it is a fact well established, that 

 fruitful intercourse may take place when the female is in a state of narcotism, 

 of somnambulism, or even of profound ordinary sleep. It has been sup- 

 posed by some that the os uteri dilates, by a kind of reflex action, to receive 

 the semen ; but of this there is but little evidence. The introduction of a 

 small quantity of the fluid just within the vagina, appears to be all that is 

 absolutely necessary for conception ; for there are many cases on record in 

 which pregnancy has occurred, in spite of the closure of the entrance to the 

 vagina by a strong membrane in which but a very small aperture existed. 

 That the spermatozoa make their way towards the ovarium, and fecundate 

 the ovum either before it entirely quits the ovisac or very shortly afterwards, 

 appears to be the general rule in regard to the Mammalia ; and their power 

 of movement must obviously be both vigorous and long continued to enable 

 them to traverse so great an extent of mucous membrane, especially when 

 it is remembered that they ascend in opposition to the direction of the ciliary 

 movement of the epithelial cells, and to the downward peristaltic action of 

 the Fallopian tubes, which may generally be noticed in animals killed soon 

 after sexual intercourse. We shall now consider the changes in the Ovum 

 and its appendages, by which it is prepared for fecundation. 



744. Up to the period when the Ovum is nearly brought to maturity, it 

 remains in the centre of the ovisac or inner layer of the Graafian follicle ; 

 and it is supported in its place by the " membrana grauulosa," which is con- 

 tinuous with its proligerous disk. The movement of the ovum towards the 

 surface, which has been already referred to as a -part of the changes by 

 which it is prepared for fecundation, appears from the observations of Val- 

 entin to be due to the following cause: In the immature ovisac, the space 

 between its inner layer and the ovum is for the most part filled up with cells ; 

 these, however, gradually dissolve away, especially on the side nearest the 

 surface of the ovary ; whilst an albuminous fluid is effused from the deeper 

 part of the ovisac, which pushes the residual layer (forming the discus pro- 

 ligerus) before it, and thus carries it against the opposite wall. At the same 

 time, there is a gradual thinning away of the various envelopes of the Graa- 

 fian follicle, as well as of its own walls, in the situation of its most projecting 

 part ; and thus it is preparing to give way at that point, for the discharge of 

 the contained ovum. Before rupture takes place, however, the ovisac itself 



1 The glands of Duverney, which were very accurately described by Professor 

 Tiedeman (1840), and subsequently by M. Huguier in the Archives d'Anatomie (1847), 

 seem to be analogous to Cowper's glands, and like them are sometimes wanting and 

 differ in size. In advanced age they are said to diminish in size, and even to disap- 

 pear. They are present in the females of all animals, where Cowper's glands exist in 

 the males. They secrete a thick, tenacious, grayish-white fluid, which is emitted in 

 large quantity at the termination of the sexual act, most likely from the spasmodic 

 contraction of the constrictor vaginae muscle, under which they lie. _Its admixture 

 with the male semen has been supposed to have some connection with impregnation ; 

 but no proof whatever has been given that any such admixture is necessary. It seems 

 not improbable, however, that it may serve, like the prostatic fluid of the male, to 

 give a dilution to the seminal fluid that is favorable to its action ( 731). These glands 

 were probably known to the ancients; and 'it is doubtless their secretion which Hip- 

 pocrates and others describe as the female semen. 



