CORPUS SPONGIOSUM URETHRA. 



531 



the middle of the cavernous structure, distributing offsets ; and the rest 

 pierce the fibrous case along the dorsum of the penis. 



In the anterior they divide into branches, which ramify in the trabeculae 

 (fig. 184, a), becoming finer, until they terminate in very minute branches, 

 which open into the veins in the intertrabecular spaces without an inter- 

 vention of capillaries. Some of the finest twigs end in tufts of short, 

 slightly curled and dilated vessels the helicine arteries of Miiller (fig. 

 184, e), which project into the intertrabecular spaces, and are imbedded 

 in the thin coat of the veins (/) : with the extremities of these twisted 

 vascular bodies fine fibrous processes are connected. The helicine arteries 

 exist in greatest number at the posterior part of each corpus cavernosum. 



The veins fill the interstices of the areolar structure, and anastomose 

 freely together to form venous plexuses ; and into them the terminal 

 branches of the arteries pour their contents. By means of the apertures 



Fig. 184. 



MAGNIFIED VIEW OF THE TRABECDLAR STRUCTURE AND ARTERIKS OF THE PENIS. 



a. Branch of an artery and its ramifications e. A tuft of the twisted or helicine arteries, 

 in the bands of the spougy structure of The dark shadowing,/, represents a vein 



the penis, b. . incasing the bundle of vessels (Miiller). 



c. Trabecular structure. 



in the septum the veins of opposite sides communicate freely. The erec- 

 tile condition of the corpus cavernosum is produced by the distension of 

 the plexuses. 



The chief veins of the corpus cavernosum escape at the crus penis with 

 the artery, and join the pudic vein ; but others issue along the upper and 

 under aspects, to end in the dorsal vein and the prostatic plexus. 



Corpus spongiosum urethrce (fig. 179). This constituent part of the 

 penis surrounds the urethra, but not equally on all sides; for at the bulb 

 only a thin stratum is above the canal, whilst at the glans penis (fig. 181, 

 /) it is placed chiefly above the urethral tube. Posteriorly an offset of 

 the corpus spongiosum is continued beyond the bulb around the urethra 



Structure. The tissue of the corpus spongiosum is similar to that of the 

 corpus cavernosum : thus it consists of a fibrous tunic inclosing a trabecu-. 

 lar structure and bloodvessels. 



The fibrous covering is less dense and strong than in the corpora cav- 

 ernosa, and consists only of circular fibres. A septal piece (fig. 179, 6 ) 

 projects inwards from it in the middle line, opposite the tube of the urethra ; 



