IQiS 



HUMAN ANATOMY. 



before piercing the superficial layer, gives off the artery to the bulb. This latter 

 artery may come off from the accessory pudic when that vessel is present (page 8i8), 

 and will then be more anterior, and less exposed to division in lithotomy, than 

 usual ; or it may come off from the internal pudic before the latter has penetrated 

 the superficial layer of the triangular ligament, and will then be behind its usual 

 position and more likely to be wounded. When the superior or deep layer of the 

 triangular ligament is opened, the prostate — partly covered by the median fibres of 

 the levator ani — and the neck of the bladder are exposed (Fig. 1631). this deep layer 

 being continuous with the prostatic sheath. 



It will be seen that in reaching this point by dissection there will have been 

 exposed certain alternating layers of fascial and muscular structures (Cunning- 

 ham) as follows : (a) superficial fascia (superficial an^ deep layers) ; (d) super- 

 ficial perineal muscles ; (c) inferior or superficial layer of the triangular ligament 



Fig. 1628. 



Crus penis 



CoUes's fascia 

 Triang. ligament 



Tuber ischii' 



Sphincter ani 



Levator ani 



Greater sacro- 



sciatic ligament 



Coccyx 

 Gluteus maximus' 



Ischio-cavemosus muscle, 

 turned aside 



Crus penis 



Dorsal artery of penis, artery of 

 corpus cavernosum to the right 

 Bulb of penis 



Superficial perineal artery 

 Superficial perineal nerves 



■Tuber ischii 



Dorsal nerve of penis 



Perineal division of 



pudic nerve 

 Internal pudic artery 



Inf. hemorrhoidal nerve 



Inferior hemorrhoidal 

 artery 



Dissection of perineum, showing inferior layer of triangular ligament 

 and inner wall of ischio-rectal fossa partially exposed. 



Cfascia trigoni urogenitalis inferior) ; (d) compressor urethrse muscle ; (e) superior 

 or deep layer of the triangular ligament (fascia trigoni yrogenitalis superior (/) 

 levator ani muscle ; ( ^) prostatic fascia (sheath). 



Landmarks. — With the patient in the lithotomy position: (i) The pubis, 

 coccyx, tuberosities, ischio-pubic rami, and greater sacro-sciatic ligaments may be 

 felt. (2) The transverse diameter, between the tuberosities, is 9 cm. (3)^ in.) ; 

 the antero-posterior diameter, from the coccyx to the pubis, is also 9 cm. (3^ in.) 

 on the skeleton, 10 cm. (4 in.) as measured on the living person. (3) The centre 

 of the anus is about 4 cm. (i}4 in. ) from the tip of the coccyx, and is on a line drawn 

 between the tips of the ischial tuberosities. (4) The perineal centre is approxi- 

 mately 4. cm. (ij4 in.) in front of the anus. (5) The bulb (and its artery) are just 

 anterior to this ; its position may be indicated by a slight median surface elevation ; 

 the artery passes inward between the layers of the triangular ligament about a half 



