356 THE ORGANS 



muscle cells, which anastomose to form a coarse meshed network, 

 the spaces of which are lined with endothelium. The spaces are 

 known as cavernous sinuses, and communicate with one another, and 

 with the blood-vessels of the penis. In the flaccid condition of the 

 organ these sinuses are empty and their sides are in apposition. In 

 erection these sinuses become filled with venous blood. 



The arteries have thick muscular walls and run in the septa. A 

 few of them open directly into the venous sinuses. Most of them 

 give rise to a superficial capillary network beneath the tunica albu- 

 ginea. From this capillary plexus the blood passes into a plexus of 

 broader venous channels in the periphery of the erectile tissue, and 



:4.- -V ■ • , ■'..^ 'A'- •_:''- 



,-> b 



,' §s'--- ■■ ■■■■,"■ 



|)-' ■ ■ a, ■ ■'•-..,■ >. -; 



Fig. 248. — Erectile Tissue of Corpus Spongiosum of Human Penis. X60. a 

 Trabeculse of connective tissue and smooth muscle; h, cavernous sinuses; c, groups of 

 leucocytes in sinus. 



these in turn communicate with the cavernous sinuses. The usual 

 direct anastomosis between arterial and venous capillaries also occurs. 

 The blood may therefore pass either through the usual course — arte- 

 ries, capillaries, veins — or, under certain conditions, may pass through 

 the cavernous sinuses. This determines the flaccid or the erect con- 

 dition of the organ. The veins arise partly from the capillaries and 

 partly from the cavernous sinuses. They pass through the tunica 

 albuginea and empty into the dorsal vein of the penis (Fig. 247). In 

 the corpus spongiosum there is probably no direct opening of arteries 

 into sinuses. Both trabecular and sinuses are also smaller. 



Of the lymphatics of the penis little definite is known. 



The nerve endings, according to Dogiel, consist of: {a) free sensory 

 endings, (i) deeply situated genital corpuscles, (c) Pacinian corpus- 



