MUSCLES AND FASCLE OF THE PERINEUM. 103 



Besides closing the orifice of the rectum it will draw the bulb 

 of the urethra backwards, or the point of the os coccygis for- 

 wards. 



The Musculus Coccygeus, 



Belongs to the interior of the pelvis. It arises by a small, 

 tendinous, and fleshy beginning, from the spine of the ischium, 

 and, lying on the anterior face of the anterior sacro-seiatic li- 

 gament, it is inserted into the side of the last bone of the sa- 

 crum, and of all those of the os coccygis. 



It draws the os coccygis forwards. 



It frequently happens that there is on each side a small fasci- 

 culus of muscle arising from the inferior bone of the sacrum in 

 front, and inserted into the bones of the coccyx; it is called 

 Sacro-Coccygeus. 



A large quantity of adipose and cellular matter exists on the 

 side of the rectum, between it and the parietes of the pelvis, 

 concealing the perineal surface of the levatores ani muscles. 



The Musculus Levator Jlni, 



Arises, fleshy, from the back of the pubes near its symphysis, 

 and from near the superior margin of the foramen thyroideum 

 above the obturator internus muscle. It also arises from the 

 aponeurosis pelvica, where this membrane is extended as a 

 thickened semi-lunar chord from the superior margin of the thy- 

 roid foramen towards the spinous process of the os ischium, 

 This second part of the origin of the leva tor ani is defectively 

 described in most books on anatomy, It is then seen to cross 

 obliquely, as far as the spine of the ischium, that portion of the 

 obturator internus which arises from the plane of the ischium. 



From this extensive origin the fibres converge and descend 

 backwards,, and have three distinct places of insertion; the pos- 

 terior fibres are inserted into the two last bones of the os coccy- 

 gis; the middle, and by far the greater number, are inserted 

 into the semi-circumference of the rectum between its longitu- 

 dinal fibres and the circular fibres of the sphincter ani; and, 

 finally, the most anterior fibres pass obliquely downwards and 

 backwards on the side of the yesical end of the membranous 



