1040 SURGICAL ANATOMY OF THE PERIN2EUM. 



The muscles brought in bo view by the removal of the superficial fascia are, 

 on each side, the accelerator urinss, erector penis, and transversus perinsei. 

 Between these muscles is a depression, in which access may be gained to the 

 membranous part of the urethra, without wounding the erectile tissues of 

 the penis, viz., the corpus spongiosum urethrse with its bulbous enlarge- 

 ment on the one hand, and the crus of the corpus cavernosum on the other, 

 covered respectively by the accelerator urinse and the erector penis. Along 

 this depression is placed the superficial artery of the perinseum, with the 

 accompanying nerve, and the transverse artery crosses behind it ; at the 

 bottom of the depression, after the muse alar structure has been turned 

 aside, the deep perineal fascia is met with. 



The last-named membrane, deep perineal or subpubic fascia (p. 260), fills 

 the upper part of the subpubic arch, and is therefore necessarily triangular 

 in shape. It consists of two laminae of fibrous membrane, the anterior 

 being much the more fibrous of the two. The layers are separated by an 

 interval, in which the constrictor muscle of the urethra (p. 265) is lodged, 

 together with Cowper's glands and the arteries of the bulb, as well as the 

 pudic arteries and nerves for a short space. Where it is perforated by the 

 membranous portion of the urethra, the fore part of the deep perineal fascia 

 is continuous with the fibrous cover of the bulb and corpus spongiosum 

 urethrse, so that the fascia does not present a defined edge to the tube 

 which passes through it. The posterior layer is connected with the capsule 

 of the prostate gland. 



The anterior of the two layers constituting the deep perineal fascia, is the struc- 

 ture recognised by most anatomical writers as forming the triangular ligament of the 

 urethra. (See especially Camper, Demonstrationes Anatomico-Pathologicae.) It is 

 pierced by the urethra, and it alone interferes with the passage of instruments along 

 the canal. 



The structure next met with in examining the perinseum is the levator 

 ani (its fore part), and immediately under that muscle is the prostate. Of 

 this gland it is here necessary only to state, as material to the present ob- 

 ject, that placed before the neck of the bladder (when the perinseum is in 

 the position required for the performance of lithotomy), around the urethra, 

 behind and below the arch of the pubes, and above the rectum, the prostate is 

 supported by the levator ani and the pelvic fascia, the 'latter descending 

 from the pubes on its upper surface. It is invested with a fibrous covering, 

 and on this account the outer surface does not readily yield to a cutting 

 instrument, while the proper substance of the gland may be incised with 

 comparative facility. From the increase of its breadth towards the lower 

 surface, it follows that the greatest extent of incision from the urethra, 

 without wholly dividing the gland, would be made in a direction outwards 

 and backwards. 



The examination of the prostate by the surgeon is made through the 

 rectum. It is only through the gut that it can be felt. When the gland 

 is enlarged, as it commonly is in aged persons, the urethra is raised above 

 its natural level and elongated. But the augmentation of size may be 

 partial, affecting one lateral lobe (a rare occurrence), and then the urethra 

 is inclined to one side ; or the middle and posterior part or middle lobe 

 may be projected upwards at the orifice of the urethra, so as even to ob- 

 struct the escape of urine from the bladder. In this last case the point of 

 the instrument passed along the urethra, must be inclined upwards more 

 than is required in the healthy condition of the parts, in order that it may 



