STRUCTURE OF THE CORPUS SPONGIOSUM. 959 



less distinctly, a subdivision into two lateral portions or lobes, separated by 

 a slight furrow on the surface, and by a slender fibrous partition within, 

 which extends for a short distance forwards ; in early infancy this is more 

 marked. It is above this part that the urethra, having pierced the tri- 

 angular ligament, enters the bulb, surrounded obliquely by a portion of 

 the spongy tissue, named by Kobelt the colliculus bulbi, from which a layer 

 of venous erectile tissue passes back upon the membranous portion of the 

 urethra, and also upon the prostatic part, to the neck of the bladder, lying 

 closely beneath the mucous membrane. At first the urethra is nearer the 

 upper than the lower part of the corpus spongiosum, but it soon gains and 

 continues to occupy the middle of that body. 



Structure. This is essentially the same as that of the corpora caver- 

 nosa, only more delicate, or with a much less quantity of the fibrous 

 trabecular structure. Like the corpora cavernosa, it is distended with blood 

 during erection ; but never acquires the same hardness. The outer fibrous 

 tunic is much thinner, is less white in colour, and contains more elastic 

 tissue ; the areoloe are smaller, and directed for the most part with their 

 long diameter corresponding to that of the penis ; the trabeculas are finer 

 and more equal in size ; and the veins form a nearly uniform plexus 

 between them ; in the glans, the meshes of this plexus are smallest and 

 most uniform. Immediately surrounding the canal of the urethra, and, 

 again, forming part of the external coat of the spongy substance, there 

 are plain muscular fibres, which are continuous posteriorly with those of 

 the bladder. The helicine arteries are found in the spongy body, except- 

 ing in the part which forms the glans penis. A considerable artery derived 

 from the internal pudic enters the bulb on each side, and supplies the 

 greater part of the spongy body, sending branches as far as the glans penis, 

 which, however, is chiefly supplied by the arteria dorsalis. Besides these, 

 Kobelt describes, as constantly present, another but much smaller branch of 

 the pudic artery, which, he says, enters the bulb on the upper surface, about 

 an inch from its posterior extremity, and runs forwards in the corpus spongi- 

 osum to the glans. Veins issue from the glans and adjoining part of the 

 spongy body, to end in the vena dorsalis penis ; those of the rest of the 

 spongy body for the most part pass out backwards through the bulb, and 

 end in the prostatic and pudic venous plexuses : some emerge from beneath 

 the corpora cavernosa, anastomose with their veins, and end partly in the 

 cutaneous venous system of the penis and scrotum, and partly in the pudic 

 and obturator veins. 



The lymphatics of the penis form a dense network on the skin of the 

 glaus and prepuce, and also underneath the mucous lining of the urethra. 

 They terminate chiefly in the inguinal glands. Deep-seated lymphatics are 

 also described as issuing from the cavernous and spongy bodies, and passing 

 under the pubic arch with the deep veins, to join the lymphatic plexuses in 

 the pelvis. 



The nerves of the penis are derived from the pudic nerve and from the 

 hypogastric plexus of the sympathetic (pp. 671 and 703). They terminate 

 by frequent division, and present indistinct traces of the so-called corpuscula 

 tactus ; on the glans and bulb of the urethra, some fibres of the cutaneous 

 nerves end in Pacinian bodies. 



URETHRA OF THE MALE. 



The male urethra extends from the neck of the bladder to the extremity 

 of the penis. Its total length is about eight inches and a half, but varies 



