70 HEALTH AND DISEASE 



For the most part the penis is made up of three elongated parallel 

 bodies, the " corpora cavernosa " and the " corpus spongiosum ". 



The two "corpora cavernosa" (b, fig. 226) commence behind in two 

 tapering processes called the crurce, which, after uniting together at the 

 root of the penis, continue forward to form the body, and terminate in 

 two rounded extremities over which the glans penis fits like a cap. 



AVhen divided transversely, the corpora cavernosa are seen to be sur- 

 rounded by a dense fibrous coat of considerable thickness. Although 

 closely united together at their circumference, they are partly separated 

 by an imperfect septum or partition, which, when viewed laterally, some- 

 what resembles the teeth of a comb; hence it has been termed the "septum 

 pectiniforme" . The partition is derived from the outer fibrous coat, and 

 becomes more 'and more complete as it reaches the root of the penis. The 

 interior of the corpora cavernosa is divided into a number of small cells 

 by a net-work of elastic septa, which interlace each other in all directions, 

 and give the divided surface the appearance of a sponge. At the time of 

 erection all the spaces so formed are filled with blood, their elastic walls 

 are put on the stretch, and the volume of the organ is correspondingly 

 increased. 



When the l)lood leaves the cells erection ceases. 



The arteries of the corpora cavernosa are derived from the pudic. 



Corpus Spongiosum. — This, the smaller of the three bodies com- 

 posing the penis (g, fig. 226), is situated in a groove which runs along the 

 lower border of the corpora cavernosa. Behind, it commences at the peri- 

 neum in an enlargement termed the " bulb ", and terminates in front in an 

 expanded free extremity, which during erection resembles the rose of a 

 watering-can. This is the " glans penis ". 



The corpus spongiosum is composed of a loose erectile tissue, similar in 

 appearance to that of the corpora cavernosa, but of much finer texture. 

 The urethral canal, by which the urine is conveyed from the bladder, is 

 surrounded by it for the greater part of its length, and a thin muscle 

 (accelerator urinae) encloses the whole from the ischial arch behind as far 

 forward as the glans. 



This muscle, by compressing the urethra from Ijehind forward, expels 

 the last few drops of urine after the efforts of the bladder have ceased. 



The Prepuce (l, fig. 226), commonly spoken of as the "sheath", is a 

 double layer of loose skin folded inward to form a recess in which the free 

 portion of the penis is enclosed. 



The inner fold of the prepuce, although continuous with the outer skin, 

 partakes of the character of mucous membrane. It is thin, supple, vascular, 

 and freely lubricated with an unctuous greasy matter, secreted by numerous 



