PLATE LIX. 

 THE SECOND VIEW OF THE PERINEUM. 



In this dissection the deep layer of the superficial fascia (Colles's) has been re- 

 moved to expose the structures lying between it and the anterior layer of the triangular 

 ligament, while on the left side the crus and erector penis muscles have been cut 

 through to expose completely the anterior layer of the ligament. 



Between the fascia of Colles and the anterior layer of the triangular ligament the 

 following structures are contained : the trausversus perinei muscles behind ; the crura 

 and erector muscles along the rami ; in the middle line the accelerator urinro covering 

 the bulbous portion of the corpus spongiosuin ; and the superficial pcrineal vessels and 

 nerves. 



The central fixed point of the perineum is situated about an inch in front of the 

 anus, and is the meeting-place of the following structures : the transversus perinei, 

 levator ani, accelerator urinte, and sphincter ani muscles ; the latter is the most super- 

 ficial, and is attached about this point to the fascia of Colles and the subcutaneous 

 tissue. This central point is important clinically, for a knife sunk hi the centre line and 

 carried a little backwards and upwards would open up the membranous urethra, and it 

 is just behind this point that the knife is entered in perinea! lithotomy. 



The levator ani was primarily a depressor of the tail, but atrophy of that organ and 

 the enlargement of the pelvic outlet have modified the muscle. Its hinder part, attached 

 to the coccyx, ia the coccygeus muscle, while the rest forms a diaphragm for the pelvic 

 outlet. The superficial sphincter is also a subcaudal slip segmented frcm the levator 



(Macalister). 



