598 CORPUS SPONGIOSUM. ERECTILE TISSUE. 



The Corpus cavernosum is distinguished into two lateral portions 

 (corpora cavernosa), by an imperfect septum and by a superior and 

 inferior groove, and is divided posteriorly into two crura. It is firmly 

 adherent, by means of its crura, to the rami of the ossa pubis and 

 ischia. It forms, anteriorly, a single rounded extremity, which is 

 received into a fossa in the base of the glans penis; the superior 

 groove lodges the dorsal vessels of the organ, and the inferior receives 

 the corpus spongiosum. Its fibrous tunic is thick, elastic, and ex- 

 tremely firm, and sends a number of fibrous bands and cords (tra- 

 beculae) inwards from its inferior groove, which cross its interior in a 

 radiating direction, and are inserted into the inner walls of the tunic. 

 These trabeculae are most abundant on the middle line, where they 

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

 and constitute the imperfect partition of the corpus cavernosum, called 

 septum pectiniforme. 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 pos- 

 terior extremity 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 sur- 

 rounds 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, enclosed 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 

 considerable proportion into the composition of the organs of genera- 

 tion. It consists essentially of a plexus of veins so closely convoluted 

 and interwoven with each other, as to give rise to a cellular appear- 

 ance when examined upon the surface of a section. The veins form- 

 ing 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 capillaries 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. 



