558 



THE TISSUES. 



Development of spermato- 

 zoids in the spermatophori of 

 the rabbit, a. Parent cell with 

 five nuclei, b. Each nucleus 

 containing a spermatic fila- 

 ment (spermatozoid). c. Nu- 

 cleus with spermatozoid. d. 

 A parent cell with several 

 spermatozoids set free from 

 the nuclei, or cells of develop- 

 ment, and coiled together in a 

 bundle. 



Fig. 387. tubes, some of them still being collected in 



bundles. The process of development is 

 usually concluded in the lower part of the 

 epididymis, though transitional forms are 

 sometimes found in the vas deferens. 



The pure semen, as found in the vas defe- 

 rens, consists of a very small quantity of a 

 viscid fluid, together with the spermatozoids 

 just spoken of; and for a description of 

 which we refer to page 207, and Fig. 116. 

 Semen, as emitted, contains the secretions of 

 the vesiculas seminales, and of Cowper's and 

 the prostate gland, in addition to the two 

 elements before mentioned. The movements 

 of the spermatozoids are not exhibited, or 

 slightly if at all, in the pure sernen of the 

 vasa deferentia ; but are first seen in the less 

 concentrated contents of the vesiculaB seminales. In the semen of 

 patients who have suffered attacks of double epididymitis, the 

 spermatozoids have remained absent for months, and even years. 

 (Gfosselin.) In those broken down by seminal losses, they are im- 

 perfectly developed, the tails being rough, irregular, and indistinct. 

 (LaUemand.) Henle states that the spermatozoids move at the rate 

 of 1 inch in 7J minutes. 



The ejaculation of the semen is principally secured by the strong 

 muscular layer of the vasa deferentia, their action being also con- 

 tinued by the vesiculas seminales, the very muscular prostate, and 

 the layers of smooth muscle inclosing the urethra ; to which must 

 also be added the action of the striated muscles, levator ani, accele- 

 rator urinae, &c. The erection of the penis is caused, Kolliker main- 

 tains, by the relaxation of the smooth muscular fibres contained in 

 the trabeculae of that organ, and the consequent flaccid state of the 

 venous sinuses and their distension with blood. This is not, how- 

 ever, a satisfactory explanation. The distension of the sinuses of 

 the corpora cavernosa and the corpus spongiosum with blood is, 

 apparently, the immediate cause of erection; this, doubtless, over- 

 coming the contractile force of the smooth muscular fibres in the 

 walls of the trabecube for the time being. 



