ANATOMICAL FEATURES 13 



the two musculo-connective tissue compartments, whereas the median raphe 

 of the scrotum denotes the area of fusion of the two cutaneous coverings of 

 the body-wall outpushings (fig. 6). 



Consequently, passing inward from the superficial perineal fascia of the 

 skin or outer wall, one finds the following tissue layers surrounding the testis: 



( 1 ) The external spermatic fascia represents the modified fascia of the ex- 

 ternal oblique muscle layer of the embryo. 



(2) The middle spermatic fascia is a modification of the internal oblique 

 muscular layer, whose tissue forms the cremaster muscle loops within 

 the scrotum (fig. 6). (Some of the cremasteric musculature may be 

 derived from the transversus layer.) 



( 3 ) The internal spermatic fascia or tunica vaginalis communis is derived 

 from the transverse muscle layer of the embryo. 



(4) Along the inner surface of the tunica vaginalis communis is the peri- 

 toneal membrane. The latter is reflected back over the surface of the 

 suspended testis, and thus forms the visceral peritoneal covering of 

 the testis. This lining tissue of the common vaginal tunic and the 

 peritoneal membrane which covers the testis are derived from the 

 original peritoneal evagination into the scrotal pocket; as such it 

 forms the tunica vaginalis propria. 



b. General Structure of the Testis 

 The testis is composed of the following structural parts: 



( 1 ) The inner layer of the tunica vaginalis propria, the tunica vaginalis 

 internus, envelops the testis. The cavity between the outer and inner 

 layers of the tunica vaginalis propria is the inguinal bursa. Oblitera- 

 tion by injury or infection of this inguinal bursa may cause degen- 

 erative changes in the testis. In other words, the testis normally must 

 be free to move within its serous (peritoneal) cavity. 



(2) Within the tunica vaginalis internus of the testis is a thick fibrous 

 layer of connective tissue, the tunica albuginea (fig. 7). From this 

 tunic, connective tissue partitions, the septula of the testis, extend 

 inward and converge toward that testicular zone where supplying 

 blood vessels enter and leave, including the lymphatics. The latter 

 zone is known as the mediastinum testis and it represents a regional 

 thickening of the tunica albuginea. Here the connective tissue fibers 

 form a latticework which acts as a framework for the larger blood 

 and lymph vessels and efferent ducts of the testis. The testis is attached 

 to the scrotal wall in the mediastinal area. 



(3) The spaces between the various septula partitions form the septula 

 compartments. In the human testis there are about 250 septula com- 

 partments, each containing a lobule of the testis. The lobuli testis 



