ERECTILE TISSUE URETHRA. 537 



tney are ranged vertically, side by side, somewhat like the teeth of a comb, 

 and constitute the imperfect partition of the corpus cavernosum, called 

 septum pediniforme. This septum is more complete at its posterior than 

 towards its anterior part. 



The tunic of the corpus cavernosum consists of strong longitudinal fibrous 

 fasciculi, closely interwoven with each other. Its internal structure is 

 composed of erectile tissue. 



The Corpus spongiosum is situated along the under surface of the corpus 

 cavernosum, in its inferior groove. It commences by its posterior extre- 

 mity between and beneath the crura penis, where it forms a considerable 

 enlargement, the bulb, and terminates anteriorly by another expansion, the 

 glans penis. Its middle portion, or body, is nearly cylindrical, and tapers 

 gradually from its posterior towards its anterior extremity. The bulb is 

 adherent to the deep perineal fascia by means of the tubular prolongation 

 of the anterior layer, which surrounds the membranous portion of the 

 urethra ; in the rest of its extent the corpus spongiosum is attached to the 

 corpus cavernosum by areolar tissue, and by veins which wind around 

 that body to reach the dorsal vein. It is composed of erectile tissue, en- 

 closed by a dense fibrous layer, much thinner than that of the corpus 

 cavernosum, and contains in its interior the spongy portion of the urethra, 

 which lies nearer its upper than its lower wall. 



Erectile tissue is a peculiar cellulo-vascular structure, entering in con- 

 siderable proportion into the composition of the organs of generation. It 

 consists essentially of a plexus of veins so closely convoluted and inter- 

 woven with each other, as to give rise to a cellular appearance when ex- 

 amined by means of a section. The veins forming this plexus are smaller 

 in the glans penis, corpus spongiosum, and circumference of the corpus 

 cavernosum, than in the central part of the latter, where they are large and 

 dilated. They have no other coat than the internal lining prolonged from 

 the neighbouring veins ; and the interstices of the plexus are occupied by 

 a peculiar reddish fibrous tissue. They receive their blood from the ca- 

 pillaries of the arteries in the same manner with veins generally, and not 

 by means of vessels having a peculiar form and distribution, as described 

 by Miiller. The helicine arteries of that physiologist have no existence. 



Vessels and Nerves. The arteries of the penis are derived from the in- 

 ternal pudic ; they are, the arteries of the bulb, arteries of the corpus 

 cavernosum, and dorsales penis. Its veins are superficial and deep. The 

 deep veins run by the side of the deep arteries, and terminate in the in- 

 ternal pudic veins. The superficial veins escape in considerable number 

 from the base of the glans, and converge on the dorsuin penis, to form a 

 large dorsal vein, which receives other veins from the corpus cavernosum 

 and spongiosum in its course, and passes backwards between two layers 

 of the ligamentum suspensorium, and through the deep fascia beneath the 

 arch of the os pubis, to terminate in the prostatic and vesical plexuses. 

 ^ The Lymphatics terminate in the inguinal glands. The Nerves are de- 

 rived from the internal pudic nerve, from the sacral plexus, and, as shown 

 by Professor Muller, in his beautiful monograph, from the hypogastrh: 

 plexus. 



URETHRA. 



The urethra is the membranous canal extending from the neck of the 

 bladder to the meatus urinarius. It is curved in its course, and is com- 



