382 



DISSECTION OF THE PELVIS. 



rectum : the opposite surface is in great part covered by the small 



saci'O-sciatic ligament, to which it is closely united. The upper 

 and borders; border is contiguous to the pyrifonnis muscle, vessels and nerves 



intervening ; and the lower meets the levator ani. 

 use. Action. This muscle helps the levator ani in supporting and 



raising the floor of the pelvis : it may also draw the coccyx slightly 



forwards. 



The LEVATOR ANI (fig. 143, D, also fig. 92, p. 241) is a thin 



flat muscle, which is attached above to the side of the pelvis, and 



descends into the outlet of the cavity, where it joins its fellow and 

 situation; supports the viscera. 



Levator 

 ani : 



origin from 

 pubis, 



triangular 

 ligament, 



ischial 

 spine, 



and pelvic 

 fascia ; 



insertion 

 into central 

 point of 

 perineum, 



FIG. 143. SIDE VIEW OF THE MUSCLES IN THE OUTLET OF THE PELVIS 

 (ILLUSTRATIONS OF DISSECTIONS). 



Muscles : 



A. Gluteus maximus, cut. 



B. Ilio-psoas, cut. 

 c. Coccygeus. 



D. Levator ani. 



E. External sphincter. 



F. Ejaculator urinse. 



G. Ischial spine, cut off. 

 H. Triangular ligament. 



Arteries : 

 a. External iliac artery, cut. 



b. External iliac vein, cut. 



c. Obliterated hypogastric. 



d. Upper, and e, lower vesical. 

 /. Internal pudic. 



Nerves : 



1. Great sciatic. 



2. Inferior hsemorrhoidal and peri- 

 neal of pudic. 



3. Dorsal nerve of penis. 



It arises anteriorly by tendinous fasciculi from the back of the 

 pubis along an oblique line in front of the obturator interims (fig. 139); 

 and below this some fleshy fibres often spring from the upper surface of 

 the triangular ligament. Posteriorly it is attached to the lower and 

 inner part of the ischial spine (fig. 139) ; and between these osseous 

 attachments the muscle takes origin in the angle between the obtura- 

 tor and recto- vesical portions of the pelvic fascia (along the curved 

 line * * in fig. 142). From this wide origin the fibres converge, 

 the anterior being directed backwards, and the posterior downwards 

 and inwards, to be inserted in the following manner : The most 



