THE SEXUAL ORGANS. 243 



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- organising 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 pro- 

 cesses; but I have no objection to offer, should the chemical 

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

 and the functions of the semen be referred to the category of 

 catalytic phenomena. 1 



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 defer entia, 

 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 remarkable 

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

 nales, the highly muscular prostate, and, of course, the trans- 

 versely striated muscular tissue of the urethra and penis. 

 Erection is caused, as I have shown (' Wiirzb. Verh/ Bd. II.), 

 by a relaxation of the muscular elements in the trabecule 



1 [The later, most important researches of Dr. Neilson, respecting the impregna- 

 tion of the ovum in Ascaris mystax ('Phil. Transact.,' 1852), and of Mr. Newport 

 (op. cit.), with regard to that of the Frog, in which he has been compelled to aban- 

 don 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 substance of the vitellus in large numbers, 

 where they underwent changes, and finally disappeared — render much of the above 

 speculation on the subject of their influence in impregnation futile. "Whatever may 

 be the nature of the influence conveyed to the vitellus by the spermatic filameuts, 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 substance 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 describes, much more resemble those noticed by 

 Von Wittich and Carus in the ovum of Spiders. — Eds.] 



