CORPUS SPONGIOSTJM ERECTILE TISSUE. 535 



The penis is composed of the. corpus cavernosum and corpus 

 spongiosum, and contains in its interior the longest portion of the 

 urethra. 



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, with the ramus of the os 

 pubis and ischium. 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 infe- 

 rior receives the corpus spongiosum. Its fibrous tunic is thick, 

 elastic, and extremely firm, and sends a number of fibrous bands 

 and cords (trabeculae) 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, some- 

 what like the teeth of a comb, and constitute the imperfect partition 

 of the corpus cavernosum, called the septum pectiniforme. This 

 septum is more complete at its posterior than towards its anterior 

 part. 



The tunic of the corpus cavernosum consists of strong longitu- 

 dinal 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 extremity between and beneath the crura penis, where 

 it forms a considerable enlargement,, the bulb, and terminates an- 

 teriorly by another expansion, the glans penis. Its middle portion, 

 or body, is nearly cylindrical, and tapers gradually from its pos- 

 terior towards its anterior extremity. The bulb is adherent to the 

 deep perineal fascia by means of the tubular prolongation of the an- 

 terior 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 cellular tissue, and by veins which wind 

 around that body to reach the dorsal vein. It is composed of erec- 

 tile tissue, enclosed by a dense fibrous tissue, much thinner than that 

 of the corpus cavernosum, and contains in its interior the spongy 

 portion of the urethra, which lies nearer to its upper than to its lower 

 wall. 



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

 considerable proportion into the composition of the organs of gene- 

 ration. It consists essentially of a plexus of veins so closely con- 

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

 appearance when examined upon the surface of a section. The 

 veins forming this plexus are smaller in the glans penis, corpus spon- 

 giosum, 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 



