PELVIS 595 



changes which occur in the state of the distension of the 

 bladder. It is a matter of importance to notice that the 

 prostate lies loosely in its sheath. Only in the middle line, in 

 front, and around the urethra as it emerges from the gland, is 

 there any degree of adhesion between the prostate and its 

 fascial envelope (Fig. 224). 



Within the sheath, and attached more closely to its inner 

 surface than to the prostate, is a plexus of thin - walled 

 veins, the pudendal plexus (Fig. 223). The plexus is spread 

 over the anterior border and the lateral surfaces of the 

 prostate, and is denser in the latter situation than in the 

 former. It receives the dorsal vein of the penis, it com- 

 municates with the internal pudendal vein, and it becomes 

 continuous above, at the base of the prostate, with the 

 prostatico-vesical venous plexus from which the blood is 

 drained by the inferior vesical veins. 



Immediately surrounding the prostate, and quite inde- 

 pendent of the sheath, is the fibrous capsule of the prostate. 

 This capsule varies in thickness, in some cases being ex- 

 tremely thin and in others forming a distinct cortex. In 

 association with operations for the removal of the prostate, 

 now frequently performed, it is important to notice that the 

 capsule has but very slight connection either with the venous 

 plexus or with the sheath of pelvic fascia. It is on this 

 account that the gland can be so easily shelled out from its 

 surroundings. 



The prostate presents for examination a base or superior 

 surface, an apex or inferior extremity, a posterior surface, two 

 lateral surfaces, and an anterior, rounded border. The base looks 

 upwards, surrounds the internal urethral orifice, and, in a 

 considerable part of its extent, is structurally continuous with 

 the bladder. Around the greater part of its circumference, 

 however, it is separated from the bladder by a groove in 

 which is lodged a group of thin-walled veins known as the 

 prostatico-vesical plexus. The apex abuts against the upper 

 fascia of the uro-genital diaphragm (Fig. 224). The posterior 

 surface is usually a flat triangular area which rests on the 

 anterior aspect of the rectum, but, occasionally, it is marked 

 by a median vertical groove. The two lateral surfaces rest 

 upon the levatores ani muscles, and are separated from each 

 other by the prominent rounded anterior border, from which 

 the urethra emerges immediately above the apex of the gland. 



i 38 a 



