CHAPTER IX. 



DISSECTION OF THE PERINEUM IN THE MALE. 1 



Under this section there will be described not only the perineeum 

 proper, but also the scrotum, testicle, prepuce, and penis. The dis- 

 section of all these must precede that of the hind limb and abdomen, 

 and it should therefore be begun without delay. 



THE PERINEUM. 



Position. — Place the animal on the middle line of its back, and draw 

 its hind legs upwards and outwards by ropes running over pulleys 

 fixed to the ceiling. The posterior extremity of the trunk should be 

 level with, or project slightly over, the end of the table on which the 

 subject rests. Empty the posterior part of the rectum, and stuff it 

 with tow saturated in some preservative solution. A stitch should 

 then be put through the edges of the anus. 



Surface -marking. — The deep boundaries of the permseum are those 

 of the outlet of the pelvis (page 353), but its superficial boundaries 

 are as follows : Above it is limited by the root of the tail, on each 

 side it is bounded by the semimembranosus muscle, and inferiorly it 

 is continued without any limit into the cleft between the thighs. 



On the middle line below the root of the tail is the anus. This forms 

 an eminence more pronounced in the young than in the old animal. 

 The integumental covering of the eminence is thin, puckered, and hair- 

 less ; and it is generally dark-pigmented. Passing between the rectum 

 and the root of the tail on each side, and most distinct when the latter 

 is forcibly elevated, there is a projection caused by the so-called suspen- 

 sory ligament of the rectum. Beneath the anus there can be seen or 

 felt a longitudinal prominence formed by the urethra ; and on the middle 

 line of this there is a raphe which is prolonged between the thighs. 



Directions. — Make a mesial incision through the skin for a length 

 of six inches below the anus. Carry this incision round the sides 

 of the anus, and up to the root of the tail. Make another incision 

 transversely from one tuber ischii to the other. These incisions will 

 enable sufficient skin to be raised as four triangular flaps. Around 

 the anus there is a quantity of fat, whose amount varies with the 



1 The description of the perinseum in the female is incorporated with that of the pelvis. 



