796 



GENERATION. 



able that during the unusual sexual excitement which the female generally 

 experiences after a monthly period, the action of the internal organs, attend- 

 ing and following coitus, presents the most favorable conditions for the 

 penetration of the fecundating elements. 



Union of the Male with the Female Element of Generation. In the ova 

 of certain animals, an opening, called a micropyle, has been demonstrated in 

 the vitelline membrane (Barry, Keber). This has been seen in the ova of rab- 

 bits, although its existence is to be inferred, only, in the human ovum. The 

 penetration of spermatozoids has been observed in the ova of various animals, 

 including the rabbit (Newport, Coste, Bischoff, Weil, Hensen and others). 

 Weil has seen spermatozoids wedged in the substance of the zona pellucida, 

 has added blood to a specimen under observation, and has restored the move- 

 ments of the spermatozoids while in this position. Hensen has seen twenty 

 or more spermatozoids within the zona pellucida in rabbits. The number of 



spermatozoids which penetrate the ovum, 

 according to the most recent researches on 

 fecundation in rabbits, does not seem to be 

 important, as only one spermatozoid forms 

 a direct union with the female generative 

 element. It is assumed that the processes 

 observed in rabbits nearly represent those 

 which take place in the human subject. 



In the rabbit, spermatozoids begin to 

 pass through the zona pellucida about thir- 

 teen hours after copulation (Hensen). By 

 this time the vitellus usually has become 

 somewhat shrunken and more or less de- 

 formed. There is then a space, filled with 

 a clear liquid, between the vitellus and the vitelline membrane, in which the 

 spermatozoids are seen in active movement. The vitelline mass, thus sur- 

 rounded with liquid, undergoes usually movements of rotation. These phe- 

 nomena have been described as deformation and gyration of the vitellus. 

 At about this time the germinal vesicle, according to the older writers, dis- 

 appears ; but it has been lately ascertained that this body is concerned in 

 the formation of the polar globule. The retraction of the vitellus and the 

 formation of the polar globule are independent of fecundation ; but the 

 formation of the polar globule is a process immediately preparatory to the 

 union of the male with the female generative element, and may properly 

 be described in connection with the mechanism of fertilization of the ovum. 

 As the deutoplasmic zone extends from the centre toward the periphery 

 of the ovum, the germinal vesicle is pushed outward until it reaches the 

 surface of the vitellus. It then becomes spindle-shaped ; and the granules 

 of the vitellus near the extremities of the spindle arrange themselves in the 

 form of stars, forming what has been called the double star, or diaster (Fol). 

 The extremity of the spindle which is near the surface projects and forms 

 a clear, mammillated eminence upon the vitellus. This projection becomes 



FIG. 291. Ovum of the rabbit, showing pene- 

 tration Of spermatozoids and retraction 

 of the vitellus (Hensen). 



