THE ABDOMEN 907 



covering the crus penis along the hne of the ischio-pubic ramus ; and the 

 superficial transverse perineal muscle, in the direction of a line passing inwards 

 and forwards from the tuber ischii to the central tendinous point. This last 

 muscle is often very indistinct, and in its dissection care is to be taken to 

 preserve the transverse perineal artery', which lies close to the muscle. 



The dissector should now separate the ischio-cavemosus from the bulbo- 

 cavemosus, and the deep perineal triangle \vill be thereby exposed. In the 

 area of each triangle a membrane will be seen, which represents the antero- 

 inferior layer of the triangular ligament of the urethra. Through it the 

 fibres of the compressor urethrae muscle may be visible. At this stage the 

 dissector should study the central tendinous point of the perineum, and note 

 the various muscles which are connected with it. The bulbo-cavemosus 

 muscle of one side is now to be carefully removed from the bulb of the urethra, 

 by cutting along the median raphe between the two muscles. The different 

 modes of insertion of the muscle are to be observed, and the bulb of the 

 urethra is to be studied, its relation to the triangular ligament and central 

 tendinous point being noted. The ischio-cavemosus should next be reflected, 

 and attention given to the crus penis. 



The dissector is now ready to study the triangular ligament of the urethra. 

 Its antero-inferior layer, also called the subpubic fascia or deep perineal 

 fascia, has been already laid bare in the area of each deep perineal triangle. 

 The several structures piercing it are to be noted, and it should be observed 

 that the base of this layer is joined by the fascia of Colles. This layer having 

 been studied in all its bearings, attention should be directed to the subpubic 

 ligament, which will be found close below the symphysis pubis. The antero- 

 inferior layer of the triangular hgament is now to be carefully removed, and 

 the following structures are to be dissected : the compressor urethrae, the 

 posterior fibres of which are known as the transversus perinaei profundus ; 

 the internal pudic vessels and dorsal nerve of the penis, lying close to the ischio- 

 pubic ramus ; the following branches of the internal pudic artery, namely, 

 the artery of the bulb or of the corpus spongiosum, lying usually about half 

 an inch from the base of the triangular ligament, the artery of the crus or of 

 the corpus cavemosum, and the dorsal artery of the penis ; a plexus of veins 

 lying in the compressor urethrae muscle, and receiving its tributaries from the 

 corresponding corpus cavernosum, and one half of the corpus spongiosum 

 and bulb ; and Cowper's glands, two in number, situated one at either side 

 of the middle Line, underneath the membranous part of the urethra. The 

 postero-superior or deep layer of the triangular hgament is next to be 

 dissected. It is very ill-defined, and will be found about half an inch above 

 and behind the antero-inferior layer. The structures which pierce it are to be 

 noted, and the anterior diverticulum of the ischio-rectal fossa should now be 

 studied, its floor being formed by the postero-superior layer. The mem- 

 branous part of the urethra, with the catheter lying in it, is to be examined. 

 The fibres of the postero-superior layer of the triangular ligament should be 

 cut thnDugh in order to show the anterior fibres of the levator ani. The 

 various structures which Ue between the two layers of the triangular hgament 

 are now to be carefully reviewed. 



The dissector is next to direct his attention to the internal pudic artery and 

 pudic nerve, making whatever dissection may now be necessary. The course, 

 relations, and branches of these structures are to be studied. The structures 

 which are divided in the operation of left lateral Uthotomy are to be mastered, 

 and, by way of concluding the dissection of the perineum, the dissector should 

 cut transversely downwards at the central tendinous point so as to enable 

 him to turn the anal canal and rectum well backwards. This will expose the 

 rectal surface of the prostate gland. 



Female Perineum. 



The dissector should practise passing the female catheter before the 

 subject is placed in the lithotomy position. When placed in position, he 

 should make himself familiar with the landmarks of the perineum. Its 

 three divisions are to be noted, and each constituent part of the pudendum 



