THE SEXUAL ORGANS. 637 



work upon the spermatic fluid, in which I expressed this view, in order 

 to indicate a ground for discussion, I compared its influence upon the 

 ovum to that of a nerve-fibre upon a nerve-cell, or of a magnet upon 

 iron ; and these comparisons, to which might be added the influence 

 which a part of an organism exerts upon a self-organizing exudation, or 

 an entire organism upon a part in a state of self-regeneration, still appear 

 to me the most suitable, if impregnation is in any way to be assimilated 

 with other processes ; but I have no objection to offer, should the chemi- 

 cal side of the question be advocated in preference, as by Bischoff, and 

 the functions of the semen be referred to the category of catalytic phe- 

 nomena.* 



In the act of copulation, various motile phenomena are presented, of 

 which we need discuss only those conducive to ejaculation and erection. 

 In the former the vasa deferentia, provided as they are with a colossal 

 muscular apparatus, are chiefly operative ; these organs, as Virchow 

 and I found in an executed criminal, shorten and contract with remark- 

 able energy when excited by galvanism ; as also do the vesiculce semi- 

 nales, the highly muscular prostate, and, of course, the transversely 

 striated muscular tissue of the urethra and penis. Erection is caused, 

 as I have shown (" Wurzb. Verh." Bd. II.), by a relaxation of the 

 muscular elements in the trabeculce of the cavernous and spongy 

 bodies, and of the tunica media of the arteries of those parts ; in con- 

 sequence of which the tissue, like a sponge which has been compressed, 

 expands and becomes filled with blood. The rigidity ensues so soon as 

 the muscles are completely relaxed, and the sinuses filled to the utmost, 

 without there being any necessity that the return of the blood should 

 be impeded, and the circulation stopped. It ceases when the muscles 

 again contract, the venous spaces become narrowed, and the blood is 

 expressed from them. In the act of ejaculation, the ischio-cavernosi, 



* [The later, most important researches of Dr. Neilson, respecting the impregnation of the 

 ovum in Jlscaris myslax (" Phil. Transact.," 1852), and of Mr. Newport (op. cit), with regard 

 to that of the Frog, in which he has been compelled to abandon his former opinion, that the 

 spermatozoa did not penetrate through the vitelline membrane, and has shown that, in that 

 case, as in the one so ably described by Dr. Neilson, those bodies penetrated into the sub- 

 stance of the vitellus in large numbers, where they underwent changes, and finally disap- 

 peared render much of the above speculation on the subject of their influence in impreg- 

 nation futile. Whatever may be the nature of the influence conveyed to the vitellus by the 

 spermatic filaments, it must now perhaps be regarded as an established fact, that it cannot 

 be communicated except by an immediate contact between the motile filaments and the sub- 

 stance of the vitellus, which thereupon undergoes segmentation, and the series of changes is 

 commenced, to terminate in the evolution of the embryo. Additional confirmation of the 

 same fact would be afforded by Dr. Keber's researches on the entrance of the spermatozoon 

 into the ovum of Unio ("De introitu Spermatozoorum," &c., 1852), could full reliance be 

 placed upon his results ; but this, from some investigations of our own on the same subject 

 both in Unio and in Pholas we consider extremely doubtful. The appearances he de- 

 scribes, much more resemble those noticed by Von Wittich and Carus in the ovum of Spi- 

 ders. TRS ] 



