THE ABDOMEN 863 



prostatic or anterior true ligaments of the bladder, and above the 

 attachment of the parietal pelvic fascia; (2) the internal surface of 

 the parietal pelvic fascia along the white line ; and (3) the pelvic sur- 

 face of the spine of the ischium in its lower part, below the coccygeus. 



Insertion. — (i) The side of the lower part of the coccyx ; (2) the 

 post-anal or ano-coccygeal raphe, where it meets its fellow of the 

 opposite side ; (3) the wall of the anal canal, where the fibres blend 

 with the longitudinal fibres of the gut, and ultimately pass with 

 them between the external and internal sphincter muscles to be 

 attached to the anal integument ; and (4) the pre -anal raphe, and 

 the central tendinous point of the perineum, where the muscle again 

 meets its fellow of the opposite side. 



The levator ani is a broad, flat, and thin fleshy muscle, the direc- 

 tion of which is downwards, inwards, and backwards, and with its 

 fellow of the opposite side it forms an incomplete muscular floor 

 to the pelvic cavity. It is covered on its pelvic aspect by the 

 visceral portion of the pelvic fascia, and on its perineal aspect by 

 the ajial fascia, and in this manner a separation is formed between 

 one half of the pelvic cavity and the ischio-rectal fossa of the 

 same side. 



The anterior border is free close to the body of the os pubis, but, 

 after it passes downwards and backwards upon the side of the 

 prostate gland in the male, or vagina in the female, it meets its 

 fellow of the opposite side, between the prostate gland and the 

 commencement of the membranous part of the urethra in the 

 male on the one hand, and the rectum on the other, or between 

 the vagina in the female and the rectum, the meeting taking place 

 in the pre-anal raphe. Between the anterior borders of the two 

 muscles the membranous part of the urethra in the male, and the 

 vagina in the female, emerge from the pelvic cavity. The anterior 

 or pubo-prostatic fibres are sometimes spoken of as the levator or 

 compressor prostatse. The posterior border adjoins the coccygeus 

 muscle. 



Nerve-supply. — (i) The anterior primary division of the fourth 

 sacral nerve, and (2) the perineal branch of the pudic nerve (deep 

 division). 



Action. — (i) To elevate and support the floor of the pelvis, thus 

 diminishing the vertical measurement of the abdominal cavity ; 



(2) to compress the anal canal, and so assist in expelling its contents ; 



(3) to elevate the anus ; (4) to elevate and compress the prostate 

 gland in the male, and the vagina in the female ; and (5) to flex the 

 coccyx. 



Coccygeus (ischio-coccygeus) — Origin. — (i) The pelvic surface of 

 the spine of the ischium, above the origin of the posterior fibres 

 of the levator ani, and (2) shghtly from the inner surface of the 

 parietal pelvic fascia above the ischial spine. 



Insertion. — The side of the upper two coccj^geal and lower two 

 sacral vertebrae. 



Nerve-supply. — The anterior primary divisions of the fourth and 

 fifth sacral nerves. 



