858 



THE GENEBATIVE APPARATUS. 



and slightly alkaline fluid. It contains a small quantity of Kquid matter 

 {liquor seminis), in which is an innumerable mass of spermatozoa. After 

 the semen has passed through the genital canals, it is made much more 

 aqueous by the addition of the fluids secreted by the walls of these excretory 

 ducts, or by the glands annexed to them. 



The spermatozoa, zoosperma, spermaiozoides, or spermatic filaments, are 

 little elongated bodies from ^^ to -g^ of a line in length. They have a 

 pyriform, flattened, or lancet-shaped head, and a filiform tail terminating in 

 a point ; this tail is often furnished at its origin with an enlargement, or 

 unilateral or bilateral ala. Their form is slightly modified during their 

 course through the excretory ducts. (In the different species, though 

 possessing certain fixed characters, the spermatozoa yet offer some curious 

 diversities. Some of these are well exhibited in the annexed representations 

 of these particles, found in the semen of very dissimilar animals.) 



The spermatozoa move by 

 Fig. 400. undulations of the tail (Grohe 



attributes the motion to the 

 contractile protoplasm con- 

 tained in the. head). Their 

 movements persist for several 

 days in the genital organs of 

 the female ; they are suddenly 

 arrested by water, acids, and 

 the electric spark; on the 

 contrary, they are animated 

 by alkaline fluids. (The 

 movements cease when the 

 spermatozoa are exposed to a 

 temperature of 120° Fahren- 

 heit.) These bodies are de- 

 veloped in the cells of the 

 tubuli seminiferi by a modi- 

 fication of their contents. 

 The cells (vesicles of evo- 

 lution) become round in the 

 centre of these canals, and 

 have from one to ten nuclei ; 

 the latter are elongated, and throw out a prolongation that gradually 

 extends and forms the tail of the spermatozoon. When all the nuclei are 

 thus transformed, the cell-wall ruptures and liberates the spermatozoa, which 

 ewim about in the minute quantity of fluid resulting from the destruction of 

 the cells. 



, Spermatozoon of the frog ; 2, Of the triton ; 3, Of 

 the finch ; 4, Of the field-mouse ; 6, Of the hedge- 

 hog ; 6, Sheep; a, Head with nucleus; 6, Body; 

 c. Tail. 



EXOKETOET APPARATUS OF THE SEMEN. 



1. The Epididymis and Deferent Canal. (Pigs. 397, 398, 399, 401, 402.) 

 Epididymis.— The organ thus named commences the excretory canal of 

 the testicle. It is a body elongated from before to behind, placed against 

 the upper border, and a little to the outside, of the spermatic eland. It has 

 a middle portion and two extremities. 



The middle is contracted, flat on both sides, and free outwardly • it is 

 related inwardly, to the spermatic vessels and the testicle, to which it iff 

 attached by a very short serous layer. The extremities are expanded and 

 adhere intimately to the testicle. The anterior, the largest, is named the 



