DISSECTION OF THE PERIN.EUM IN THE MALE. 293 



resemblance to the teeth of a comb ; hence the name. Besides the sep- 

 tum pectiniforme, numerous small trabecule pass into the interior of the 

 corpora cavernosa, and by their anastomosis form a framework for these 

 bodies. The trabecular are composed of fibrous tissue with some bundles 

 of non-striped muscular tissue. Between the trabecular are innumer- 

 able intercommunicating spaces, placed between the capillaries and the 

 small veins. During erection the blood is poured into these spaces, 

 and thus is brought about the increase in the size of the organ. At 

 other times the blood passes in the ordinary manner from the capillaries 

 to the venous radicles. In the crura and peripheral part of the 

 cavernous bodies some of the small arteries terminate directly in 

 these venous spaces. The small arteries are embedded in the 

 trabecular, and when these are contracted, in the non-erect state, the 

 arteries assume a coiled disposition, from which they receive the name 

 arterice helicince. 



Structure of the corpus spongiosum. The structure of the spongy 

 body resembles, somewhat, that just described. It possesses an 

 envelope of fibrous tissue with trabecular and a plexus of large veins. 

 In its peripheral part, and in the bulb, it also contains true cavernous 

 spaces, like those of the cavernous bodies but smaller. 



Structure of the spongy (or extra-pelvic) part of the urethra. This 

 should be laid open on its under aspect with scissors. The lumen of 

 the tube is not uniform. At the ischial arch (this will not be seen at 

 present) it presents a dilatation ; and its calibre is again increased as it 

 enters the glans, forming what is termed in man the fossa navicularis. 

 The interior of the tube is lined by mucous membrane having simple 

 columnar epithelium, except at its orifice, where it is stratified and 

 squamous. The ducts of numerous small racemose glands open on the 

 surface of the membrane. External to the mucous membrane the wall 

 of the urethra is made up of non-striped muscular tissue, arranged as an 

 inner circular and an outer longitudinal layer. 



