214 SURGICAL ANATOMY OP 



superficial fascia, inferior hsemorrhoidal vessels and 

 nerves, which lie superficially in the anterior part of the 

 ischio-rectal fossa, transversus perinei muscles and ves- 

 sels, and superficial perineal vessels and nerves. The 

 structures divided on the staff are the lower part of the 

 triangular ligament, deep transversus urethrse muscle ; 

 the deep part of the incision divides the membranous 

 urethra, the substance of the prostate, and vessels 

 around it. 



Structures to be Avoided. The bulb, or the rectum, 

 which stands a risk of being wounded, if the first inci- 

 sion be too near the middle line; the internal ptidic 

 artery, if on the other hand the deep incision be made 

 too far externally ; the artery to the bulb, if it be made 

 too far forward; and the entire breadth of prostate, with 

 its capsule, and the ejaculatory ducts, if it be carried too 

 far backwards or downwards. 



If the entire breadth of the gland and its capsule were 

 divided, the urine would be infiltrated beneath the peri- 

 toneum. 



The depth of the perineum between the neck of the 

 bladder and the integument varies from rather more 

 than an inch to four inches, and between the tuberosities 

 of the ischium from two inches or less, to four. 



In the child, the pelvis being narrow, the perineum is 

 narrow also ; and the neck of the bladder comparatively 

 high up, whilst the peritoneum descends very low be- 

 tween the bladder and the rectum. The bladder itself is 

 more conical in shape, and is rather an abdominal than 

 a pelvic viscus, and its connection^ with the surrounding 

 parts are very loose. Hence the difficulty experienced 

 in getting into the bladder in lateral lithotomy in chil- 

 dren, and the danger of pushing the prostate before the 



