418 A MANUAL OF ANATOMY. 



Insertion. Into the tip of the coccyx, into the median 

 raphe extending from the coccyx to the anus, into the 

 lateral surfaces of the rectum, also into the median raphe 

 as far forward as the tendinous centre of the perineum. In 

 the female the anterior fibres of the muscle are attached to 

 the side of the vagina. 



Nerve Supply. Inferior hemorrhoidal, fourth and fifth 

 sacral. 



Action. To elevate the pelvic floor and rectum, prostate 

 (vagina) and bladder. To diminish the pelvic cavity, thus 

 compressing the abdominal viscera, and aid in all expulsive 

 efforts. The levator ani and the coccygeus have been 

 called the pelvic diaphragm, as their combined action 

 resembles the action of the diaphragm. 



Coccygeus. 



Origin. From the inner surface of the spine of the 

 ischium. 



Insertion. Into the side of the coccyx and the last two 

 pieces of the sacrum and the lateral ligaments connecting 

 the two bones. 



Nerve Supply. Fourth and fifth sacral and the coccygeal. 



Action. Draws the coccyx forward and aids the leva- 

 tor ani. 



DISSECTION. 



Remove the levator ani, cutting it away at its origin and insertion. 



Consult the description of the rectovesical fascia, page 399. 



Draw the rectum backward, and keeping close to it cut the fascia between 

 it and the prostate and bladder until the rectovesical fold of peritoneum is 

 reached. Clean the prostate and base of bladder. 



The Prostatic Plexus. 



This is a plexus situated within the capsule of the pros- 

 tate and between the rectovesical fascia and the neck of the 

 bladder. 



