The Perineum. 297 



an ischio-rectal abscess the incision should be made in a 

 longitudinal direction and a little nearer to the ischium 

 than to the rectum so as to avoid wounding the latter. 



In fistula in ano the opening in the rectum is, as a rule, 

 within one and a half inches (generally half an inch) 

 from the margin of the anus, because of the slanting posi- 

 tion of the levator ani muscle which directs the pus, down- 

 wards and inwards, towards the interval between this 

 muscle and the internal sphincter. The fistulous channel 

 may be straight or tortuous, and, should two openings be 

 found externally, it will be advisable to divide the sphinc- 

 ter ani muscles at one point, only, since there is a possibil- 

 ity that permanent loss of function might result were two 

 divisions of the muscles made. 



Lateral Lithotomy. After the patient has been brought 

 into the lithotomy position, a staff is introduced into the 

 bladder and held with the handle well over the patient's 

 abdomen, so that the curve of the staff will push the mem- 

 branous portion of the urethra towards the surface of the 

 perineum. The first incision is made by inserting the 

 knife a little to the left of the median line and just behind 

 the central tendinous point of the perineum, i.e., the knife 

 should enter about one and a quarter inches in front of 

 the centre of the anus. The knife thrust should be at 

 right angles to the perineum and directed towards the 

 staff, and the incision should be completed by carrying the 

 knife downwards and outwards through the left ischio- 

 rectal fossa, to end at a point between the tuber ischii and 

 the posterior part of the anus, one-third nearer to the 

 tuberosity than to the anus. The incision should be about 

 three inches in length and should gradually become more 

 shallow as it is made backwards. The staff is now drawn 

 upward so that its hollow will rest against the pubic arch, 

 the forefinger of the left hand feels for the groove in its 



