THE TUNICA VAGINALIS. 



443 



obliterated, from the internal abdominal ring down nearly to the 

 testicle, leaving no trace but the indistinct fibrous cord already de- 

 scribed, while the lower part remains as a closed serous sac sm-rounding 

 the testicle, and which is thence named the tunica vaginalis. 



In the female foetus an analogous pouch of peritoneum descends for 

 a short distance along the round ligament of the uterus, and has 

 received the appellation of the canal of Nuck. Of this traces may 

 almost always be seen in the adult. 



Varieties. — The neck of the processus vaginalis sometimes becomes closed at 

 intervals only, leaving a series of sacculi along the front of the cord ; or a long 

 lioucli may continue open at the upper end, leading fi'om the abdominal cavity into 

 the inguinal canal. In other instances, the peritoneal process remains altogether 

 pervious, and the ca-\aty of the tunica vaginalis is thus made continuous with 

 that of the peritoneum. In such a case of congenital defect, a portion of 

 intestine or omentum may descend from the abdomen into the inguinal canal 

 and scrotum, and constitute what is named a congenital hernia. Lastly, one 

 or both testes may remain pennanently within the abdomen, or their descent may 

 be delayed till after puberty, when it may occasion serious disturbance. Retention 

 of the testes in the abdomen (cry|>torchismus) is, in many instances, the accom- 

 paniment of arrested development of the glandular structure ; it is, however, a 

 peculiarity which may be present without impotence. 



In a few mammals, as the elephant, the testes remain permanently within the 

 abdomen ; in a much larger number, as the rodentia, they only descend at each 

 period of rut. The com- 



plete closure of the tunica 

 vaginalis is peculiar to man, 

 and may be considered as 

 connected with his adapta- 

 tion to the erect posture. 



Fig. 317. — The Left Tunica 

 Vaginalis opened, sho'sv- 

 ING THE Testis, Epididy- 

 mis, &C., FROM THE OUTER 

 SIDE. (A. T.) 



J), p, the cut edges of the 

 jiarietal tunica vaginalis drawn 

 aside laterally, as well as above 

 and below ; t, the body of the 

 testicle ; e, the globus major 

 of the epididymis ; e', the 

 globus minor, near which, /, a. 

 fold of the tunica vaginalis (or 

 ligament) passes from the 

 body of the testis to the side ; 

 in the upper part of the figure 

 the tunica vaginalis has been 

 slightly dissected off at the 

 place of its reflection on the 

 cord to show v d, the vas 

 deferens, and [;, the organ of 

 Girakles ; G-, the three small 

 nodules of this organ enlarged 

 about ten times, and showing 

 the remains of tubular struc- 

 ture within them ; h, hydatid 

 of Morgagni. 



Fig. 317. 



-^ 



6. The tunica vaginalis. — This tunic forms a shut sac, of which the 

 opposite free surfaces are in contact with each other. Like the serous 



