THE REPRODUCTIVE SYSTEM. 643 



In the fine connective tissue which supports the tubules of the testis 

 are to be found flattened and nucleated epithelial cells, probably the re- 

 mains of the Wolffian body. The lymphatics of the testes are numerous, 

 and may be injected by inserting the needle of an injecting syringe into 

 the tunica albuginea, and pressing in the injection with slight effort. 



Vesiculae Seminales. The vesiculcB seminales have the appear- 

 ance of outgrowths from the vasa deferentia. Each vas deferens, 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; and this branch dilating, variously branching, and 

 pursuing in both itself and its branches a tortuous course, forms the 

 vesicula seminalis. 



Structure. Each of the vesiculas may be unravelled into a single 

 branching tube, sacculated, convoluted, and folded up. The structure 

 of the vesiculas resembles closely that of the vasa deferentia. The mu- 

 cous membrane lining the vesiculse seminales, like that of the gall-bladder, 



FIG. 433. From a section of the testis of dog, showing portions of seminal tubes. A, seminal 

 epithelial cells, and numerous small cells loosely arranged; B, the small cells or spermatoblasts 

 converted into spermatozoa; C, groups of these in a further stage of development. (Klein.) 



is minutely wrinkled and set with folds and ridges arranged so as to give 

 it a finely reticulated appearance. 



The Penis. The penis is composed of three long more or less 

 cylindrical masses, inclosed in remarkably firm fibrous sheaths, of which 

 two, the corpora cavernosa, are alike, and are firmly joined together, and 

 receive below and between them the third part, or corpus spongiosum. 

 The urethra passes through the corpus spongiosum. The penis is at- 

 tached to the symphysis pubis by its root. The enlarged extremity or 

 glans penis is continuous with the corpus spongiosum. The integument 

 covering the penis forms a loose fold from the junction of the glans with 

 the body, called the prepuce or foreskin. 



Structure. (a) The urethra is lined by stratified pavement epithelium 

 in the prostatic portion; in front of the bulb the epithelium becomes 

 columnar, whilst at the fossa navicularis it is again lined with stratified 

 pavement epithelium. The mucous membrane consists chiefly of fibrous 

 connective tissue, intermixed with which are many elastic fibres. It is 



