PARTS IN OUTLET OF PELVIS. 



501 



It meets its fellow inferiorly, but the muscles of opposite sides are sepa- 

 rated in front by the urethra, with the vagina in the female ; and the inter- 

 val between them is closed by the triangular ligament of the perineum, H. 

 The COCCYGEUS MUSCLE (fig. 173, c ) is flat and triangular, and assists 

 to close the outlet of the pelvis. It arises from the upper part of the 

 ischial spine, and some fibres are attached to the small sacro-sciatic ligament. 

 Widening as it passes inwards the muscle is inserted into tlie side, and the 

 contiguous anterior surface of the coccyx, and into the side of the lower 

 piece of the sacrum. 



Fig. 173. 



SIDE VIEW OF THE MUSCLES IN THE OUTLET OF THE PELVIS (Illustrations of Dissections). 



Muscles : 



A. Gluteus maximus, cut. 



B. Psoas and Iliacus, cut. 

 c. Coccygeus. 



D. Levator ani. 



E. External and sphincter. 



F. Ejaculator urinse. 



Q. Ischial spine, cut off. 

 H. Triangular ligament. 



Arteries : 



a. External iliac artery, cut. 



b. Its accompanying vein. 



c. Obliterated hypogastric cord. 



d. Upper vesical, and 



e. Lower vesical. 

 /. Internal pudic. 



Nerves : 



1. Sacral plexus. 



2. Inferior hemorrhoidal. 



3. Pudic. 



The inner surface looks to the pelvis, and is in contact with the rec- 

 tum on the left side; the opposite surface rests on the small sacro-sciatic 

 ligament. The upper or hinder border is contiguous to the pyriformis 

 muscle, vessels and nerves intervening ; and the anterior or lower border 

 is parallel with the levator ani muscle. 



Action. Uniting in its action with the hinder fibres of the levator ani, 

 the muscle will draw slightly forwards the coccyx. 



The LEVATOR ANI (fig. 173, D ) is a thin flat muscle, which is attached 

 above to the side of the pelvis, and descends below into the outlet of the 

 cavity, where it joins its fellow and supports the viscera. 



It arises anteriorly by fleshy fibres from an oblique line above the ob- 

 turator internus ; lower down from the fascia on that muscle, and from the 

 back of the triangular ligament. Posteriorly it is fixed to the lower and 

 inner surface of the iscliial spine. And between those osseous attach- 

 ments the muscle takes origin from the under part of the recto-vesical fas- 

 cia, but not in a straight line. All the fibres are directed downwards to 



