388 



DISSECTION OF THE PERINEUM. 



boundary the pudic vessels nd nerve should be denuded: they lie in a 

 canal formed by fascia, and at some distance from the surface. 



On the right side it is not necessary to clean the muscular fibres, when 

 following the vessels and nerves. If the student begins at the outer bor- 

 der of the sphincter, he will find the inferior hoemorrhoidal vessels and 

 nerve, which he may trace outwards to the pudic trunks: some of the 

 branches, which join the superficial perinatal and inferior pudendal nerves, 

 aiv to be followed forwards. In the posterior angle of the space seek a 

 small offset of the fourth sacral ne^ve ; and external to it, one or more 

 branches of the sciatic nerve and vessels turning round the border of the 

 glutens. Near the front of the fossa is a superficial perinaeal artery and 

 nerve (of the pudic) ; and the last, after communicating with the haemor- 

 rhoidal nerve, leaves the fossa. A second perinaeal nerve with a deeper 

 position may be found at the front of the hollow. 



The ISCHIO-RECTAL FOSSA (fig. 129) is the space intervening between 

 the rectum and the ischial part of the innominate bone. It is a somewhat 



Fig. 129. 



A VIEW OF THE DISSECTION OF THE RKCTAL HALF OF THE PERINJECTM. (Illustrations of 



Dissections.) 



Muscles : 



A. External sphincter. 



B. Corrugator cutis, only part left. 

 c. Internal sphincter. 



D. Levator ani. 



E. Gluteus maximus. 



Arteries : 



a. Trunk of the pudic artery. 



&. Inferior hsemorrhoidul. 



c. Branches of the sciatic. 

 Nerves : 



1. Inferior hsemorrhoidal. 



2. Superficial pcrinteal. 



3. Perinaal branch of the fourth sacral. 



4. Small sciatic. 



conical interval, uncovered by muscle, which is larger behind than before, 

 and diminishes in width as it sinks into the pelvis. Its widtli is about 

 one inch at the surface; and its depth about two inches at the outer part. 

 It is filled by a soft granular fat. 



