DISSECTION OF THE PERINEUM IN THE MALE. 277 



and it passes transversely inwards to terminate on the middle line over 

 the urethra, being confounded with its fellow of the opposite side, and 

 with the first fibres of the accelerator urinse. 



Action. — To dilate the bulbous part of the urethra. 



The Accelerator UriNyE. These muscles (right and left) cover the 

 sides and lower face of the urethra from the ischial arch to the free 

 extremity of the penis. Along the inferior median line of that tube the 

 right and left muscles are joined by an intermediate fibrous raphe. 

 From this raphe the fibres pass round the urethra on each side, with a 

 slightly forward inclination, and are lost on the upper aspect of 

 the tube, but without reaching the middle line. Beneath the anus the 

 first fibres of the muscle seem to arise from the retractor penis muscle, 

 but elsewhere the retractor is superficial to the intermediate raphe of 

 the right and left muscles. 



Action. — The muscles of opposite sides always act together ; and when 

 they do so, they diminish the calibre of the urethra and expel its con- 

 tents. In this way they are instrumental in the ejaculation of semen. 

 In micturition the muscles ordinarily do not come into play until the 

 close of the act, when they empty the urethra from behind to before. 

 The necessity for this action exists because the expelling power of the 

 bladder is lost as soon as its own cavity is emptied. 



The Erector Penis. This is a thick, dark-red muscle covering the 

 crus penis. Its fibres arise from the inferior ischiatic spine (of the 

 tuber), and they terminate on the crus. 



Action. — To aid in erecting the penis by compressing the crus and 

 thus retai-ding the return of blood from the cavernous body of the 

 penis. 



the scrotum (plate 37). 



Position. — Let the subject remain in the dorsal position, but unfasten 

 the rope from one of the hind limbs, and allow the trunk to incline to 

 the same side. The loose limb should be fastened backwards out of the 

 way. 



Directions. — Grasp the neck of the scrotum close to the wall of the 

 abdomen, so as to tighten the skin over the testicle, and then tie a piece 

 of soft cord round the constricted neck of the scrotum. This will facili- 

 tate the dissection of the different layers of the pouch. 



The scrotum is the bag, or pouch, in which the testicles are sus- 

 pended. It is laminated, and comprises the following layers : — 



1. The Scrotal Integument. This is continuous with the surround- 

 ing skin, of which it is a modified portion. It is thin, with short fine 

 hairs, and numerous sebaceous glands, whose secretion renders it moist. 

 It is traversed mesially by a raphe, continuous posteriorly with the 

 median raphe of the perinseum. The scrotal integument forms a single 

 bag for the two testicles. 



