448 PROCESS OF FECUNDATION. [sect. 201. 



in a fruitful intercourse), up to the ovum and into its substance. 

 That the spermatozoa are the proper fecundating elements of the 

 semen, has been placed beyond the slightest doubt by the obser- 

 vations of Prevost and Dumas, Schwann and Leuckart, on the 

 semen after filtration, and, above all, by the recent discoveries of 

 Newport (Philos. Trans., 1853, ii. p. 233). The last-named author 

 also establishes the fact, that the spermatozoa actually penetrate 

 the substance of the ovum, as was asserted many years before by 

 Barry, and on this point, various subsequent observers have con- 

 firmed the statements of Newport (on the rabbit and frog, in fishes 

 and insects). Now that we are acquainted with the passage of the 

 spermatozoa into the ovum, we can no longer regard their fecund- 

 ating power as being a dynamic influence, as was formerly supposed, 

 from the circumstance that moving filaments alone can fecundate ; 

 on the contrary, it now appears probable that the material of the 

 spermatozoa becomes actually mingled with the yelk, and thus 

 renders it capable of development. Let it be remembered, how- 

 ever, that we are still far from being in a position to maintain a 

 similar penetration of the ovum by the spermatozoon in the whole 

 animal series, so that we must be careful how we put forth any 

 theory of fertilisation as being equally applicable in all cases. 



The ejaculation of the semen is effected in the main by the vasa 

 defcrentia, with their powerful muscular apparatus. These organs 

 have been seen by Virchoic and myself, on the body of an executed 

 criminal, to contract and shorten with remarkable energy under 

 the influence of galvanism ; and the same action is witnessed in 

 the seminal vesicles, the very muscular prostate, and .the striated 

 muscular fibres of the urethra and penis. The erection of the 

 penis is effected, as I have shown ( Wurz. Verh., vol. ii.), by a relax- 

 ation of the muscular fibres in the trabecular of the cavernous and 

 spongy bodies, and in the middle coat of the arteries of those parts ; 

 as a consequence of this relaxation, the spongy tissue, like a sponge 

 which has been compressed, dilates and fills itself with blood. 

 Rigidity appears as soon as the muscular fibres are entirely re- 

 laxed and the venous sinuses completely filled, without there being 

 any need for the return of blood being impeded, or the circulation 

 stopped. It disappears when the muscies contract again, the 

 venous spaces becoming narrow, and the blood being pressed out 

 of them. In an executed criminal, we have recently found very 

 energetic contraction, upon the application of electric stimuli to 

 the exposed spongy tissue of the corpora cavernosa. During the 

 ejaculation of the semen, the ischio-cavernosi and the bulbo- 



