CHAPTER IX. 



DISSECTION OF THE PERINJEUM IN THE MALE.i 



Under this section there will be described not only the perinseum proper, 

 bnt also the scrotum, testicle, prepuce, and penis. The dissection 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-marlcing. — The deep boundaries of the perinseum 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 sufiioient 

 skin to be raised as four triangular flaps. Around the anus there is a 

 quantity of fat, whose amount varies with the condition of the subject, 



^ The description of the perinseum in the female is incorporated "witli that of the pelvis. 



