1124 



SURGICAL AND TOPOGRAPHICAL ANATOMY 



wards into the scrotum and penis, it loses its fat, and contains dartos fibres. The 

 deeper layer, found only over the urethral triangle, is called the fascia of Colles 

 (tig. 693). Attached at the sides to the rami of the pubes, behind to the base of 

 the triangular ligament, and open in front, it forms a somewhat triangular pouch, 

 containing the sui)erficial vessels, nerves, and muscles, the bulb, and adjacent part 

 of the urethra. Owing to this space being closed behind and open in front, and to 

 its containing the above structures, fluids extravasated within this space will 

 obviously tend to make their way forwards into the scrotum, penis, and lower part 

 of the al)dominal wall. * 



The urethra. — This can be examined in part with the finger, but much better 

 with the aid of a sound. The anterior, or penile, part is movable; the posterior, 

 or deeper, more fixed. It is narrowest at the meatus and where the membranous 

 urethra passes through the triangular ligament. It is widest in the prostatic part 



Fig. 692. — Deep Dissection of Male Perinjcum. (Roser.) 



The bulb is slightly raised and the rectum drawn backwards, in order to make clear the 

 membranous urethra and prostate, which are shown incised as in the lateral operation of 

 lithotomy. 



Erector pems^ 



Wilson's m 



URETHRA DIVIDED A- 

 THE LATERAL INCi- 



Artery to bulb (abnorma! 



PROSTATE GLAND, WITH ITS — 

 PLEXUS OF VESSELS 

 S'iperficial perinceal 



artery 

 Levantor aril, its 

 anterior fibres raised 

 to show the prostate 



Gluteus maxim 



'imlinuation of internal 



piidir artery 

 ^ Anterior layer of 

 " triangular ligament 



1 / tery to bulb 



-COWPER'S GLAND 



INCISION IN THE PROSTATE 

 GLAND AS IN THE LATERAL 



OPERATION 

 -TransversuB perinaei 

 muscle 



- Trunk oj internal pudic 



^RECTUM 



.External sphincter 



and the fossa navicularis. One of the most important landmarks is the triangular 

 ligament, the base of which can just be felt in a thin perinseum. The meml)ranous 

 urethra passes through this, about three-quarters of an inch above the central jioint 

 of the perina^um, about the same distance below the subpubic ligament, or an inch 

 below the symphysis. Above the urethra run the dorsal vessels and nerves of the 

 penis. The fixation, undilatability, surrounding muscular fibres, and close neigh- 

 bourhood of a large amount of erectile tissue (the bulb), all account for difficulties 

 in introducing instruments past this point. It is here also that the urethra is most 

 liable to be damaged by a fall or blow. The attachment of the deep layer of 

 superficial fascia to the base of the triangular ligament accounts for the fact that 

 urine extravasated from a ruptured urethra, or through an opening behind a 

 stricture, passes usually not backwards into the anal triangle, but forwards into 

 the scrotum and abdominal wall. The other structures in relation with the trian- 

 gular ligament are shown in fig. 693. 



