THE PROSTATE 1389 



the membranous urethra may here give additional difficult}^ in the passage of 

 a catheter. 



False passages most commonly occm* through the floor of the bulb on account of this, 

 difiiculty in entering the membranous urethra. The point of a small catheter may also be 

 caught in the following apertm-es: (1) The lacuna magna in the roof of the fossa navicularis 

 of the glandular urethra; (2) other crypts or lacuna? in the penile part, mostly situated in the 

 upper wall; (3) the prostatic sinus in the floor of the prostatic m-ethra about its centre. With 

 the penis raised the urethra presents a simple curve under the symphysis with the proportions 

 of an ordinary silver catheter. 



It is in the region of the uro-genital diaphragm that the urethra is most liable to be damaged 

 by a fall or blow, and the urine extravasated as a result will be beneath Colles's fascia. In 

 rupture of the membranous m-ethra urine may find its way in front of the inferior fascia of the 

 uro-genital diaphragm .by coexisting injury to this, or through openings in the vessels, etc.; 

 in a few such cases urine will make its way backward behind the fascia into the space of 

 Retzius, ascending thence between the peritoneum and transversahs fascia. The attachment 

 of the deep layer of superficial fascia to the base of the uro-genital diaphragm accounts for the 

 fact that urine extravasated from a ruptured urethra or through an opening behind a stricture 

 passes not backward into the anal triangle, but forward onto the scrotum and abdominal wall. 



The prostate consists of a mass of racemose glandular tubules imbedded 

 in a fibro-muscular stroma, that surrounds the first part of the urethra and lies 

 below the neck of the bladder. Its base is intimately connected ^\^th the bladder 

 by the continuation of vesical and urethral mucous membrane and bj' the inser- 

 tion of the outer longitudinal muscular coat of the bladder into the gland. The 

 inner circular muscle fibres of the bladder become specialised round the internal 

 urethral orifice to form the internal sphincter. 



Adenomatous enlargements of the gland usually grow upward through this sphincter which 

 is thus dilated and pushed aside, so that the glandular growth is covered only by vesical mucous 

 membrane. 



The apex of the prostate lies at the level of the lower border of the pubic 

 symphysis and 1.5 cm. behind it. It is firmly fixed to the superior fascia of the 

 uro-genital diaphragm (deep layer of the uro-genital trigone) and here the urethra 

 leaves it to become the membranous part. The anterior surface directed 

 verticall}' lies 2 cm. behind the lower part of the pubic s^'mphysis in relation to 

 the prostatic plexus of veins; and from it the dense pubo-prostatic ligaments 

 run forward on either side to the pubes. The posterior surface is in contact with 

 the rectum, through the anterior wall of which it may be palpated 4 cm. (1^ in.) 

 above the anal margin. It is separated from the rectum by the two layers of 

 the recto-vesical septum (Elliot Smith).* The lateral surfaces are supported 

 by the anterior fibres of the levator ani, from which, however, they are separated 

 on each side by a dense mass of fibrous tissue in which the pudendal (prostatic) 

 plexus of veins is imbedded. 



The prostatic urethra traverses the gland nearer the anterior than the pos- 

 terior surface, with a slight forward concavit3^ Its floor is placed posteriorly 

 and presents an eminence, the coUiculus seminalis, about the centre of which is 

 the orifice of the prostatic sinus, on either side of which open the common ejacu- 

 latory ducts. The prostate is indefinitely divided into two lateral lobes. The 

 fissure uniting them across the middle line in front of the urethra (the anterior 

 commissure) is fibro-muscular and contains no glandular tissue. Behind the 

 urethra the lateral lobes are continuous and the portion of gland lying between 

 bladder, ejaculatory ducts and urethra has been erroneously termed the "middle 

 lobe." Though not a separate lobe anatomically, adenomatous hypertrophy 

 of this part is common, when it projects up into the bladder, and prevents the 

 proper emptying of that organ. 



Capsule and sheath of the prostate. — In senile enlargement of the prostate removal may be 

 effected by the suprapubic or by the perineal route. In the former, the bladder is opened 

 above the pubes, the mucous membrane lying over the gland as it projects into the bladder is 

 scratched through behind, and with th*^ finger the whole adenomatous mass is enucleated. 

 This process usually involves tearing out the whole of the prostatic urethra, and the ejaculatory 

 ducts. The parts left behind consist of (1) the "capsule"' which is simply the outer part of 

 the gland proper stretched over the adenomatous mass, and consists of fibro-muscular tissue 

 with a few flattened glandular tubules (C. Wallace).! Outside this (2) the fibrous "sheath" 

 is derived from the visceral layer of pelvic fascia, in which is imbedded, on the anterior and 

 lateral aspects of the gland, the prostatic plexus. Since these veins are not torn there is com- 



* Studies in Anatomy of the Pelvis. Journ. Anat. and Phj'siol., vol. 42, 1908. 

 t C. Wallace. Prostatic Enlargement, 1907. 



