THE MALE COPULATIVE ORGAN. 239 



THE PENIS. 



The male copulative organ consists of three cylinders of erectile tissue 

 the paired corpora cavernosa and single corpus spongiosum united with one 

 another and invested by coverings of fascia and skin. The anterior or upper 

 and flattened surface of the penis is formed by the corpora cavernosa ; the pos- 

 terior or under surface corresponds to the corpus spongiosum, which is trav- 

 ersed by the urethra. The conical glans penis, forming the free end of the 

 organ, is continuous with the spongy body which it resembles in structure. 



Each of the cylinders of erectile tissue is enclosed by a robust sheath, 

 the tunica albuginea, composed of dense fibrous tissue, intermingled with 

 fine elastic fibres but no muscle. The sheath surrounding the corpora 



Subcutaneous tissue^ g^ Deep dorsal vein 



Skin' 



Tunica albuginea 



Superficial fascia 



Corpus cavernosuir 



Urethra " 



i,* Corpus spongiosum 



FIG. 290. Transverse section of penis of child. X 10. 



cavernosa, which includes an outer longitudinal and an inner circular layer 

 and in places attains a thickness of over i mm. , is much stronger than that 

 enclosing the spongy body; it is, however, imperfect along the opposed 

 median surfaces of the two cylinders, where it forms fat pectiniform septum. 

 From the inner surface of the tunica albuginea fibrous septa and trabeculae 

 are given off which constitute the framework supporting the vessels and nerves 

 and enclosing the characteristic blood-spaces of the erectile tissue. Numerous 

 bundles of unstriped muscle, irregularly disposed, occupy the fibrous trabeculae 

 and plates that separate the venous spaces, which are thus surrounded by 

 imperfect layers of contractile tissue. The trabecular muscle is most abundant 

 within the cavernous and spongy bodies, and least so within the glans. 



The arteries conveying blood to the erectile tissue are of two kinds: 

 those coursing within the trabeculae and nourishing the tissues, vasa nutritia, 

 and those carrying blood primarily to the venous lacunae. The latter are 



