OF THE DIFFERENT MUSCLES. 151 



THE ANAL REGION 



Includes a pair of muscles and a single one, 



RETRACTOR ANI, 



Which retracts the anus — draws it within the pelvis. 



SPHINCTER ANI, 



Which closes the anus, after the expulsion of the faeces. 



COCCYGEAL REGION 



Includes the erector coccygis. 

 Use. — To elevate the tail. 



DEPRESSOR COCCYGIS. 



Use. — To depress the tail. 



CURVATOR COCCYGIS. 



Use. —To incurvate the tail, or laterally flex it around the 

 quarters. 



COMPRESSOR COCCYGIS. 



Use. — To assist in depressing the tail, and to maintain it 

 forcibly pressed against the anus. 



MUSCLES OF THE TRUNK. 

 ABDOMINAL REGION. 



The white line, (or linea alba,) extending from the ensi- 

 form cartilage to the pubes, marks the place of junction of 

 the tendons of three pairs of muscles, and is perforated near 

 the middle by the umbilicus or navel ; through which, in the 

 foetus, passes the umbilical cord. On either side of this line 

 is another, taking a curvilinear course, called the linea semi- 

 lunaris : this is the line of demarcation between the oblique 

 and transverse muscles and their tendons, denoting where the 

 one substance begins and the other ends. Running trans- 

 versely between these are several white lines, to which the 



