1018 



THE MALE ORGANS OF GENERATION. 



Size and Weight. The average dimensions of this gland are from one and a 

 half to two inches in length, one inch in breadth, and an inch and a quarter in the 

 antero-posterior diameter, and the weight varies from six to eight drachms, the 

 left testicle being a little the larger. 



The testis is invested by three tunics the tunica vaginalis, tunica albuginea, 

 and tunica vasculosa. 



The Tunica Vaginalis is the serous covering of the testis. It is a pouch of 

 serous membrane, derived from the peritoneum during the descent of the testis in 

 the foetus from the abdomen into the scrotum. After its descent that portion of 

 the pouch which extends from the internal ring to near the upper part of the gland 

 becomes obliterated, the lower portion remaining as a shut sac, which invests 

 the outer surface of the testis, and is reflected on to the internal surface of the 

 scrotum ; hence it may be described as consisting of a visceral and parietal 

 portion. 



The visceral portion of the tunica vaginalis covers the outer surface of the 

 testis, as well as the epididymis, connecting the latter to the testis by means of a 

 distinct fold. From the posterior border of the gland it is reflected on to the 

 internal surface of the scrotum. 



The parietal portion of the tunica vaginalis is far more extensive than the 

 visceral portion, extending upward for some distance in front and on the inner side 

 of the cord, and reaching below the testis. The inner surface of the tunica vagi- 

 nalis is free, smooth, and covered by a layer of endothelial cells. The interval 

 between the visceral and parietal layers of this membrane constitutes the cavity 

 of the tunica vaginalis. 



The obliterated portion of the pouch may generally be seen as a fibro-cellular 

 thread lying in the loose areolar tissue around the spermatic cord ; sometimes this 

 may be traced as a distinct band from the upper end of the inguinal canal, where 

 it is connected with the peritoneum, down to the tunica vaginalis ; sometimes it 



gradually becomes lost on the spermatic cord. 

 Occasionally no trace of it can be detected. In 

 some cases it happens that the pouch of peri- 

 toneum does not become obliterated, but the sac 

 of the peritoneum communicates with the tunica 

 vaginalis. This may give rise to one of the 

 varieties of oblique inguinal hernia (page 1049). 

 Or in other cases the pouch may contract, but 

 not become entirely obliterated ; it -then forms 

 a minute canal leading from the peritoneum to 

 the tunica vaginalis. 1 



The Tunica Albuginea is the fibrous cover- 

 ing of the testis. It is a dense fibrous mem- 

 brane, of a bluish-white color, composed of 

 bundles of white fibrous tissue, which interlace 

 in every direction. Its outer surface is covered 

 by the tunica vaginalis, except at the points of 

 attachment of the epididymis to the testicle, and 

 along its posterior border, where the spermatic- 

 vessels enter the gland. This membrane sur- 

 rounds the glandular structure of the testicle, 

 and at its posterior border is reflected into the 



interior of the gland, forming an incomplete vertical septum, called the mediasti- 

 num testis (corpus Highmorianum). 



The mediastinum testis extends from the upper, nearly to the lower, extremity 



1 It is recorded that in the post-mortem examination of Sir Astley Cooper this minute canal was 

 found on both sides of the body. Sir Astley Cooper states that when a student he suffered from 

 inguinal hernia ; probably this was of the congenital variety, and the canal found after death was 

 the remains of the one down which the hernia travelled (Lancet, 1824, vol. ii., p. 116). 



Spermatic cord. 



Artery of 

 cord. 



Tunica vaginalis, 

 parietal layer. 



Digital 

 fossa. 



FIG. 566. The testis in situ, the tunica 

 vaginalis having been laid open. 



