THE SEMINAL FLUID 



771 



Head 



Body 



Tail 



enlargement just before it unites with its fellow. The ductus deferens has 

 muscular walls and is lined with ciliated epithelial cells. 



The Vesiculae Seminales. The seminal vesicles have the appearance 

 of outgrowths from the base of the deferent ducts. Each deferent duct 

 just before it enters the prostate gland, through part of which it passes to 

 terminate in the urethra, gives off a side branch which bends back from it at 

 an acute angle. This branch, dilating, variously branching, and pursuing in 

 both itself and its branches a tortuous course, forms the vesicula seminalis. 

 Each vesicle is a single-branching, convoluted, and sacculated tube. The 

 microscopic structure resembles closely that of the ductus deferens. 



The Penis. The penis is attached to the symphysis pubis by its root. 

 It is composed of three long, more or less cylindrical masses enclosed in 

 remarkably firm fibrous sheaths. Two, the 

 corpora cavernosa, are alike and are firmly 

 joined together. They receive below and be- 

 tween them the third part, or corpus spongi- 

 osum. The urethra passes through the corpus 

 spongiosum. The enlarged extremity, or glans 

 penis, is continuous with the corpus spongiosum. 

 Cowper's glands are at its base, and their ducts 

 open into the base of the urethra. 



The Prostate Gland. The prostate is 

 situated at the neck of the urinary bladder, and 

 encloses the base of the urethra. The prostate 

 is made up of small compound tubular glands 

 embedded in an abundance of muscular fibers 

 and connective tissue. The glandular sub- 

 stance consists of numerous small saccules, 

 opening into elongated ducts, which unite into 

 a smaller number of excretory ducts. The 

 acini of the upper part of the prostate are 

 small and hemispherical, in the middle and 

 lower parts the tubes are longer and more 



convoluted. The ducts, twelve to twenty in number, open into the urethra. 

 They are lined by a layer of columnar cells, beneath which is a layer of 

 small polyhedral cells. 



The muscular tissue of the prostate not only forms the chief part of the 

 stroma of the gland, but also forms a continuous layer inside the fibrous 

 sheath, as well as a layer surrounding the urethra continuous with the sphinc- 

 ter of the bladder. 



The Seminal Fluid. The sperm cells of the testes are joined on their 

 way to the exterior by the fluids secreted by the mucous lining of the various 

 tubules and glands. Of the fluids the chief ones are the secretions of the 



End piece 



FIG. 491. Human Sperma- 

 tozoa (after Retzius). A, Side 

 view, B, front view. 



