1298 THE UKO-GENITAL SYSTEM. 



muscular fibres, constituting the tunica dartos, situated in the superficial fascia. 

 When this muscular layer is contracted, the scrotum becomes smaller and some- 

 what globular, and the skin is thrown into folds or wrinkles called rugae; when 

 it is relaxed, the scrotum is flaccid and pendulous, and the skin becomes more 

 smooth and even. The layer of fascia which contains the smooth muscle fibres 

 can be shown to be continuous superiorly with the superficial fascia of the penis, 

 and with the deep layer of the superficial fascia of the abdomen, and to be attached 

 laterally to the bones forming the pubic arch. The muscle fibres are arranged 

 in a thick layer of interlacing bundles, and many of the deeper fibres are continued 

 info the septum scroti, which divides the scrotum into two cavities, one for each 

 testis. The wall of each of these cavities is formed by the corresponding tunica 

 vaginalis, infundibuliform fascia, fascia cremasterica, and intercolumnar fascia; while 

 the skin, the superficial fascia, and the superficial part of the dartos muscle form 

 coverings which are common to the whole scrotum, and enclose both cavities. 

 The layer of tissue immediately beneath the dartos tunic is made up of exceedingly 

 loose and easily stretched areolar connective tissue, and in it, as throughout 

 in the superficial fascia of the scrotum, there is an entire absence of fat. 



The scrotum in the foetus contains no cavity, but, like the labia majora in the female, it is 

 composed entirely of vascular connective tissue. 



Vessels and Nerves of the Scrotum. The scrotum receives its vascular supply from the 

 posterior scrotal branches of the perineal divisions of the internal pudendal arteries, which reach 

 it from behind, and from the external pudendal branches of the femoral artery, which reach its 

 upper and anterior part. 



The nerves of the scrotum are derived on each side from the posterior scrotal branches of the 

 perineal division of the pudendal nerve, from the perineal branch of the posterior cutaneous 

 nerve of the thigh, and from the ilio-inguinal nerve. The branches from the pudendal and 

 posterior cutaneous nerves reach the scrotum from behind, while the ilio-inguinal supplies its 

 upper and anterior part. The nerve fibres for the dartos muscle fibres are believed to have their 

 origin from the hypogastric plexus. 



PENIS. 



The penis is composed chiefly of erectile tissue, and is traversed by the canal 

 of the urethra. The surface nearest to which the canal of the urethra lies is 

 called the facies urethralis, or urethral surface ; the opposite and more extensive 

 aspect is the dorsum penis. The erectile tissue is for the most part disposed 

 in three longitudinal columns, which in the body of the organ are placed side by 

 side, while at the root of the penis they separate from one another, and become 

 attached to the fascia inferior of the urogenital diaphragm and to the pubic arch. 

 Two of these masses of erectile tissue, placed one on each side of the median plane, 

 and forming the dorsum and sides of the penis, are called the corpora cavernosa 

 penis, while the third, which is called the corpus cavernosum urethrae (O.T. corpus 

 spongiosum), is situated in the median plane near the urethral surface. The corpus 

 cavernosum urethrse is the part of the penis which is traversed by the urethra. 

 and it is considerably smaller than the corpora cavernosa penis, which form the 

 chief bulk of the organ. 



In the corpus penis, or body of the penis, each corpus cavernosum penis is placed 

 close to the median plane, and presents a rounded surface, except where it is 

 flattened by contact with its fellow of the opposite side. The corpora cavernosa 

 penis are separated on the anterior or dorsal surface by a shallow groove, and OD 

 the posterior or urethral aspect by a deeper and wider furrow, in which lies the corpus 

 cavernosum urethrse (Fig. 1018). Towards the distal end of the penis the corpus 

 cavernosum urethrae appears to expand, and, spreading towards the dorsal surface oi 

 the organ, it forms a kind of conical cap, the glans penis, which covers over the blunt 

 rounded termination of the corpora cavernosa penis. The prominent margin oi 

 the glans, called the corona glandis, projects dorsally and laterally beyond the 

 extremities of the corpora cavernosa penis. The glans is traversed by the termina 

 part of the urethra, which ends near the summit of the glans in a slit-like opening 

 called the orificium urethrse externum, or external urethral orifice. The unitec 

 corpora cavernosa penis end in a blunt conical extremity, the apex of which is 



