162 



TOPOGRAPHICAL ANATOMY OF THE 



length, is closed by the contraction of the sphincter muscle and the 

 presence of mucous folds, except during the passage of faeces. 



M. LEVATOR AN I. — The flattened levator muscle of the anus arises 

 from the medial surface of the sciatic spine and the sacro-spinous 

 ligament. An oblique course in a dorsal and caudal direction carries 

 the muscle to the edge of the external sphincter of the anus under 

 which it disappears. 



Lig. sacroiliacum dorsale breve. 

 N. ischiadicus. Lig. sacroiliacum dorsale longuni. 



A. glutaea cranialis. , ] 



I I I 

 I t I 



A. glutsea caudalis. 



M. sacrococcygeus 

 dorsalis lateralis. 

 M. cocc>gcus. 



Lynipli glands. 



sphincter ani 

 externus. 



Branch of a. iliolumbalis. 



A. pudenda interna 



A. circumflexa femoris lateralis. 



A. iliaca externa 



M. (;bturatorius internus. 



Rectum. 

 N. pudendus. 



A. perinei. 



A. bulbi urethrse. 

 Mm. gemelli. 

 Tendon of m. obturatorius internus. 

 N. hsemorrhoidalis caudalis. 



Fig. 71. — Lateral aspect of the male pelvis after removal of the sacro-spinous 

 and sacro-tuberous ligaments. 



M. SPHINCTER ANI INTERNUS. — If the levator muscle of the anus 

 be reflected and the bundles of longitudinal fibres of the rectum 

 separated, a partial view of the internal sphincter muscle may be 

 obtained. This consists of pale, circular fibres in no way separable 

 from the circular muscular stratum of the wall of the rectum, of 

 which the sphincter must be regarded as a specialised part. 



M. RECTOCOCCYGEUS. — A bundle of the longitudinal fibres of the 

 rectum becomes isolated and, proceeding in a dorsal direction, ends 

 on the ventral aspect of the root of the tail. 



M. RETRACTOR PENIS. — If the terminal part of the m. levator ani 



