PE^IS. 737 



Tlie mucous membrane covering the glans penis contains no sebaceous glands ; 

 but projecting from its free surface are a number of small, highly sensitive 

 papillae. 



The penis is composed of a mass of erectile tissue, inclosed in three cylindrical 

 fibrous compartments. Two of these, the corpora cavernosa, are placed side by 

 side along the upper part of the organ ; the third or corpus spongiosum incloses 

 the urethra, and is placed below. 



The Corpora Cavernosa form the chief part of the body of the penis. They 

 consist of two fibrous cylindrical tubes, placed side by side, and intimately con- 

 nected along the median line for their anterior three-fourths, their posterior fourth 

 being separated to form the two crura, by which the penis is connected to the 

 rami of the pubes. Each crus commences by a thick-pointed process in front of 

 the tuberosity of the ischium ; and, near its junction with its fellow, presents a 

 slight enlargement, named, by Kobelt, the bulb of the corpus cavernosum. Just 

 beyond this point they become constricted, and retain an equal diameter to their 

 anterior extremity, where they form a single rounded end, which is received 

 into a fossa in the base of the glans penis. A median groove on the upper surface 

 lodges the dorsal vein of the penis, and the groove on the under surface receives 

 the corpus spongiosum. The root of the penis is connected to the symphysis 

 pubis by the suspensory ligament. 



Structure. Each corpus cavernosum consists of a strong fibrous envelop, 

 inclosing a fibrous reticular structure, containing erectile tissue in its meshes. It 

 is separated from its fellow by an incomplete fibrous septum. 



TliQ fibrous investment is extremely dense, of considerable thickness, arid highly 

 elastic ; it not only invests the surface of the organ, but sends off numerous fibrous 

 bands (trabeculae) from its inner surface, as well as from the surface of the septum, 

 which cross its interior in all directions, subdividing it into a number of separate 

 compartments, which present a spongy structure, in which the erectile tissue is 

 contained. 



The trabecular structure fills the interior of the corpora cavernosa. Its com- 

 ponent fibres are larger and stronger round the circumference than at the centre 

 of the corpora cavernosa; they are also thicker behind than in front. The inter- 

 spaces, on the contrary, are larger at the centre than at the circumference, their 

 long diameter being directed transversely ; and they are largest anteriorly. They 

 are lined by a layer of squamous epithelium. 



The Jibrous septum forms an imperfect partition between the two corpora caver- 

 nosa; it is thick and complete behind, but in front it is incomplete, and consists of 

 a number of vertical bands of fibrous tissue, which are arranged like the teeth of 

 a comb ; hence the name, septum pectiniforme. These bands extend between the 

 dorsal and urethral surface of the corpora cavernosa. 



The fibrous investment and septum consist of longitudinal bands of white fibroua 

 tissue, with numerous elastic and muscular fibres. The trabeculaa also consist of 

 white fibrous tissue, elastic fibres, and plain muscular fibres, and inclose arteries 

 and nerves. 



The Corpus Spongiosum incloses the urethra, and is situated in the groove on 

 the under surface of the corpora cavernosa. It commences posteriorly in front 

 of the deep perinea-1 fascia, between the diverging crura of the corpora cavernosa, 

 where it forms a rounded enlargement, the bulb ; and terminates, anteriorly, in 

 another expansion, the glans penis, which overlays the anterior rounded extremity 

 of the corpora cavernosa ; its central portion or body is cylindrical, and tapers 

 slightly from behind forwards. 



The bulb varies in size in different subjects ; it receives a fibrous investment 

 from the anterior layer of the deep perineal fascia, and is surrounded by the 

 Accelerator urinaB muscle. The urethra enters the bulb nearer its upper than its 

 lower surface, being surrounded by a layer of erectile tissue, named, by Kobelt, 

 the colliculi bulbi, a thin prolongation of which is continued backwards round 

 the membranous and prostatic portions of the canal to the neck of the bladder, 

 47 



