MUSCLES OF THE BODY. 137 
spine (Fig. 70, d); 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 vertebre. The fibres 
pass caudad and are inserted by tendons into the articular 
processes and the dorsal surface of the caudal vertebre. 
Action. —Extends (raises) the tail. 
M. extensor caude 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 caude medialis 
(Fig. 70, é). 
Origin in many fleshy bundles from the articular processes 
of the sacral vertebra, 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 vertebra. The muscle grows continually smaller 
as it passes caudad. 
Action.— Raises the tail. 
M. abductor caude (coccygis) externus (Fig. 68, w; Fig. 
70, ¢).—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 znserted into the transverse processes and lateral surfaces of 
the caudal vertebre, as far back as the eighth or ninth. 
Action.—Bends the tail sideways. 
M. abductor caude 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 
vertebre. - 
Relations. —Lateral surface with the caudofemoralis (Fig. 
68, s), gluteus maximus, and pyriformis. Medial surface with 
the iliocaudalis and the flexor caude longus (Fig. 68, +). 
M. iliocaudalis (Str.-D.) (Fig. 162, 1”, page 398).—This 
represents a portion of the levator ani of man, and in some 
