FECUNDATION. 497 



of the thickness of the vitelline membrane, to comprehend 

 this penetration ; though in a number of the lower animals 

 pores or canaliculi have been observed, which might afford 

 a passage for the fecundating element (micropyle). 



In a recent work 1 on fecundation and development of the 

 ovum in rabbits, Weil has assured himself that spermatozoids 

 do penetrate into the very substance of the ovum. He also 

 states that they preserve their active movements for several 

 hours after their passage through the vitelline membrane. 

 He has not only seen them during the separation of the cells 

 from the vitellus after its segmentation, but even inside the 

 protoplasm of the vitelline cells. At this latter place the 

 spermatozoids lose their outline and disappear. An examina- 

 tion of all the evidence presented would apparently prove, 

 that fecundation (conception) essentially consists in a fusion 

 of the spermatozoid with the female element. This view is 

 also supported by the comparative study of fecundation in 

 the lower vegetable life (in the spirogyra, for instance). 



Under the exciting influence of the fecundated or fertilized 

 ovum in its course of development, the uterine epithelium is 

 the seat of wonderful changes. The mucous tissue forms 

 large pouches, and, so soon as the ovum comes into the womb, 

 it is lodged in a valley formed by two of these pouches or 

 villi ; then these latter grow in every direction and finally 

 completely enclose the ovum, so that a perfect envelope 

 called the caduca (Fig. 136, c, ee, /, &), or membrana 

 decidua is formed around it. The whole of the lining 

 mucous surface of the uterus is called the caduca; that por- 

 tion which lines the uterus is called uterine caduca or decidua 

 vera (Fig. 136, c) ; that which forms a complete envelope of 

 the egg is called foetal caduca or decidua reflexa (ee,f) ; that 

 surface of this decidua reflexa which is continuous with the 

 first-named (that is, the very point of attachment of the egg 

 to the uterus) is called the caduca serotina, or decidua sero- 

 tina (Fig. 136, ee), in accordance with false ideas formerly 

 held in regard to its mode of development. The placenta 

 (Fig. 136 and 143) is formed near, and partially at the 

 expense of, the caduca serotina. 



The muscular portion of the uterus also undergoes hyper- 

 trophy, and forms new (smooth) muscular elements, simul- 

 taneously with the enlargement of preexisting fibres. Finally, 

 the vessels partake of this increase of development, as increased 



1 C. Weil, in Strieker's " Medic. Jahrbiicher, 1873. 

 32 



