246 



DISSECTION OF THE PERINEUM. 



Two super- 

 ficial peri- 

 neal ; 



external 



and internal; 



distributed 

 to scrotum 

 and penis. 



Muscular 

 branches. 



Inferior 



pudendal 



nerve 



ends in 

 scrotum. 



Dissection 

 of muscles 

 of the 



urethra and 

 penis, 



and of their 

 nerves. 



Three 

 muscles 

 over tri- 

 angular 

 ligament. 



Central 

 point, 



where 



muscles 



join. 



Erector 

 penis : 



origin ; 



insertion : 



THE SUPERFICIAL PERINEAL NERVES, two in number, are named 

 external and internal : both arise in the ischio-rectal fossa from the 

 perineal division of the pudic nerve (p. 242). 



The external branch is continued forwards, beneath the super- 

 ficial fascia, with the artery of the same name to the back of the 

 scrotum. While in the fossa the nerve gives inwards an offset to 

 the integuments in front of the anus; and this communicates with 

 the inferior haemorrhoidal nerve. 



The internal branch passes under the transverse muscle, and 

 accompanies the other to the scrotum. 



The superficial perineal branches communicate with one another, 

 and the external is joined by the inferior pudendal nerve. At the 

 scrotum they are distributed by long slender filaments, which reach 

 as far as the under surface of the penis. 



Other muscular branches of the perineal nerve will be afterwards 

 examined (p. 248). 



The INFERIOR OR LONG PUDENDAL NERVE is a branch of the 

 small sciatic. It pierces the fascia lata about one inch in front of 

 the ischial tuberosity, and enters beneath the superficial fascia of the 

 perineum, to end in the outer and fore parts of the scrotum. 

 Communications take place between this nerve, the inferior 

 hsemorrhoidal, and the outer of the two superficial perineal 

 branches. 



Dissection, For the display of the muscles, the superficial fascia, 

 as well as the vessels and nerves of the left side, must be taken 

 away from the anterior half of the perineal space. Afterwards a 

 thin aponeurotic layer is to be removed from the surface of the 

 muscles. Over the middle line lies the ejaculator urinse, or bulbo- 

 cavernosus ; along the outer edge of the space is the erector penis, or 

 ischio-cavernosus ; and behind, passing obliquely between the other 

 two, is the transverse muscle. 



On the right side the student should seek the branches of the 

 perineal nerve to the muscles. 



MUSCLES (figs. 92 and 93). Superficial to the triangular ligament, 

 in the anterior half of the perineal space, are the three muscles, viz., 

 the erector penis, the ejaculator urinoe, and the transversus perinei. 

 Another muscle of the urethra is contained between the layers of 

 the triangular ligament, and will be subsequently seen. 



Central point of the perineum. Between the urethra and the rec- 

 tum is a small transverse tendinous septum, to the centre of which 

 this name has been applied. It is placed about one inch in 

 front of the anus, and in it the muscles acting on the rectum 

 and urethra are united. Its development varies greatly in different 

 bodies. 



The ERECTOR PENIS (ischio-cavernosus) is the most external of 

 the three muscles, and is narrower at each end than in the middle. It 

 covers the cms penis : and its fibres arise from the ischial tuberosity 

 farther back than the attachment of the penis, and from the bone on 

 each side of the cms (p. 251). In front, the muscle is inserted into an 



