MUSCLES OF THE BODY. 137 



spinae (Fig. 70, ^) ; it lies next to the dorsal median line, the 

 muscles of right and left side touching one another in the 

 middle line. 



Origin by numerous fleshy bundles from the spinous 

 processes of the sacral and first caudal vertebrae. The fibres 

 pass caudad and are inserted by tendons into the articular 

 processes and the dorsal surface of the caudal vertebrae. 



Action. Extends (raises) the tail. 



M. extensor caudae lateralis (Fig. 70, /). This is a con- 

 tinuation caudad of the medial portion of the longissimus dorsi 

 (Fig. 70, a) ; it lies just laterad of the extensor caudae medialis 

 (Fig. 70, e). 



Origin in many fleshy bundles from the articular processes 

 of the sacral vertebrae, and the transverse processes of the 

 caudal vertebrae. The fibres curve dorsocaudad and are 

 inserted by many long slender tendons on the dorsal surfaces 

 of the caudal vertebrae. The muscle grows continually smaller 

 as it passes caudad. 



Action. Raises the tail. 



M. abductor caudae (coccygis) externus (Fig. 68, w\ Fig. 

 70, g}. A rounded muscle on the lateral surface of the cranial 

 part of the tail. 



Origin from the medial side of the dorsal border of the 

 ilium, and from the dorsal surface of the sacrum. The muscle 

 passes caudad, lying just ventrad of the extensor lateralis, and 

 is inserted into the transverse processes and lateral surfaces of 

 the caudal vertebrae, as far back as the eighth or ninth. 



Action. Bends the tail sideways. 



M. abductor caudae internus (or M. coccygeus). A large 

 flat muscle, having origin on the spine of the ischium. The 

 muscle passes dorsomediad, spreading out, and is inserted into 

 the transverse processes of the second to the fourth caudal 

 vertebrae. 



Relations. Lateral surface with the caudofemoralis (Fig. 

 68, s), gluteus maximus, and pyriformis. Medial surface with 

 the iliocaudalis and the flexor caudae longus (Fig. 68, x]. 



M. iliocaudalis (Str.-D.) (Fig. 162, ir, page 398). This 

 represents a portion of the levator ani of man, and in some 



