BOUNDARIES OF THE PBBINEtfM. 237 



limited, on the surface of the body, by the scrotum in front, and by 

 the thighs and buttocks on the sides and behind. 



The skin of this region is of a dark colour, and is covered with The anus, 

 hairs. In the middle line is the aperture of the anus, which is 

 Behind a line extending from the anterior part of the one ischial 

 tuberosity to the other. In front of the anus the surface is slightly 

 convex over the urethra, and presents a longitudinal prominent line 

 >r raphe, which divides the space into halves. Between the anus the raphe. 

 ind the tuberosity of the hip-bone the surface is somewhat depressed hollow on 

 >ver the hollow of the subjacent ischio-rectal fossa, especially in su 

 emaciated bodies. 



The margin of the anal aperture possesses numerous converging and folds 

 bids, but these are more or less obliterated by the position of the and V j jl ?? 



J r around that 



>ody and the distention of the anus ; and projecting oftentimes through opening. 



md around the opening are some dilated veins (haemorrhoids). 



Deep boundaries. The deep boundaries of the perineal space will Bounding 

 )e ascertained, in the progress of the dissection, to correspond with ^ tiiose'of 

 he inferior aperture or outlet of the pelvis. The limits are to outlet of 

 )e observed on a dry or prepared pelvis, on which the ligaments pe 

 emain entire ; and the student should trace on the body the 

 orresponding boundaries with his linger. In front is the symphysis 

 >ubis ; and at the back is the tip of the coccyx, with the great gluteal 

 luscles. On each side in front is the portion of the hip-bone which 

 ounds the subpubic arch, viz., from the pubic symphysis to the 

 ^chial tuberosity ; and further back is the great sacro-sciatic ligament 

 xtending from the tuberosity to the coccyx. This region sinks 

 nto the outlet of the pelvis as far" as the recto-vesical fascia, which 

 orms its floor. 



Form and size. The interval included within the boundaries above Form of the 



described is rather heart-shaped, owing to the projection of the coccyx s P ace > and 



, J measure- 

 behind ; and it measures over the surface about lour inches irorn ments. 



before backwards, and three and a half inches between the ischial 

 tuberosities. 



Depth. The depth of the perineum from the surface to the floor, D ep th of 

 which will be revealed in dissection, may be said to be generally the space, 

 about three inches between the anus and the ischial tuberosity, 

 but this measurement varies greatly in different bodies ; and it 

 amounts to about an inch at the fore part, between the pubic bones. 



Division. A line from the front of the tuberosity of one side to A line be- 

 the corresponding point on the other will divide the perineal space tutero.sitLs 

 into two parts. The anterior half (urethral) contains the root of the divides it 

 penis and the urethra, with their muscles, and vessels and nerves. 

 The posterior half (rectal] is occupied by the lower end of the large 

 intestine, with its muscles, &c. 



POSTERIOR HALF OF THE SPACE. 



This portion of the perineal space contains the lower end of the contents of 

 rectum, surrounded by its elevator muscles and the muscles acting anal half . 



