836 TEE GENESATIVE APPARATUS. 



This, in reality, is not a distinct coat, but merely the fine ramifications of 

 the spermatic artery spreading beneath the tunica albuginea, and held 

 together by delicate cellular tissue.) 



The veins are very voluminous and frequently varicose, and comport 

 themselves like the arteries ; they unite in a single trunk that enters the 

 posterior vena cava, near the renal veins. (On the cord, in addition to their 

 sometimes varicose condition, the spermatic veins have been observed to 

 form a network, named the pampiniform plexus.) 



The lymphatics are most numerous beneath the serous layer and th-e 

 timica albuginea. They commence in the lacunse between the seminal tubes 

 and vessels, and terminate in the sublumbar glands. 



The nerves of the testicle are derived from the sympathetic (and pass 

 from the abdomen with the blood-vessels) ; they form a small particular 

 plexus around the artery. (The nerves pierce the membrana propria of the 

 tubuli seminiferi, and end in a more or less pyramidal mass of protoplasm, 

 in which lie clear elliptical nuclei. The ends of the fibres, therefore, lie 

 in close proximity to the outer layer of secreting cells.) 



Development. — In the foetus, at an early age, the testicle floats in the 

 abdominal cavity, being suspended from the sublumbar region, near the flank, 

 by a wide peritoneal fold, at the anterior border of which are the spermatic 

 vessels (Fig. 399, e.) ; the tunica vaginalis is not yet present. The 

 mechanism of the formation of this is very simple, and easy to understand. 

 The visceral layer of the tunica vaginalis, which envelops the testicle and 

 the cord, being already formed, as well as the serous frsenum that establishes 

 continuity between this and the parietal layer in the adult animal, it only 

 remains to explain how nature proceeds to construct the vaginal sac in which 

 the gland is afterwards contained. 



We have remarked, that to the posterior extremity of the testicle is 

 attached a thick round funicle, the other end of which passes into the upper 

 inguinal ring, being enveloped by the peritoneum, and fixed to the posterior 

 border of the serous layer that suspends the testicle. This funicle is the 

 gubernaculum testis, and is continuous, by its inguinal extremity, with the 

 dartos, whose structure it apparently shares, and which alone acts as the 

 scrotal sac to it. The serous layer covering it has on its outer adherent 

 face the cremaster muscle, which is attached to the ilio-lumbar aponeurosis 

 in tlje vicinity of the inguinal ring, enters the serous tube formed by the 

 peritoneal envelope of the gubernaculum, and advances by its terminal 

 extremity to near the testicle. To this organ is due the principal share in 

 {he formation of the vaginal pouch. 



When the progress of development in the foetus pushes the testicle 

 towards the inguinal region, the gubernaculum acts as a guide, as its 

 picturesque name sufficiently indicates. It is the first to descend into the 

 inguinal opening, drawing the testicle after it. But in performing this 

 movement it also carries along its peritoneal covering, which gradually 

 leaves it to become related, by its adherent face, to the walls of the 

 inguinal canal ; and thus this membrane becomes reflected, just as would a 

 sock everted or turned down from the leg to the foot, the latter being 

 supposed to represent the testicle. 



The parietal layer of the vaginal sac is, then, nothing more than the 

 serous tube that, in the foetus, enveloped the gubernaculum testis while in 

 the abdomen, and which is reversed on the testicle and cord after their 

 descent into the scrotum, the cremaster muscle on its adherent face having 

 become external. 



