136 THE MUSCLES. 
ventrad of the insertion of the rectus capitis posterior medius 
for about five millimeters next to the median line. 
Relations.—Dorsal surface with the rectus capitis posterior 
medius. Ventral surface with the posterior atlanto-occipital 
membrane. 
Action.—Assists the rectus capitis posterior major. 
M. obliquus inferior (Fig. 71, 4). 
Origin from the whole lateral surface of the spine of the 
axis. The parallel fibres form a thick mass which passes 
laterad and craniad. 
fnsertion into the dorsal surface of the transverse process 
of the atlas along a narrow area near its lateral margin. 
Relations.—Outer surface with the rectus capitis posterior 
major (Fig. 71, @), the complexus (Fig. 69, 4), and the 
obliquus superior (Fig. 71, ¢). Inner surface with the axis. 
Action.—Rotates the head. 
M. obliquus capitis superior (Fig. 71, ¢; Fig. 72, e).— 
This is a triangular muscle passing from the outer border of the 
atlas laterad of the recti capitis posteriores to the occiput. 
Origin from the lateral border of the transverse process of 
the atlas on its ventral margin. The fibres pass craniad and 
diverge. 
Insertion into the caudal side of the mastoid process of the 
temporal bone and into a line parallel with the lambdoidal 
ridge and ventrad' of it, from the mastoid process to within one 
centimeter of the median line. 
Relations.—Outer surface with the splenius (Fig. 73, 4), 
complexus (Fig. 69, 4), and longissimus capitis (Fig. 73, g). 
Inner surface with the obliquus inferior (Fig. 71, 4), the wing 
of the atlas, and the rectus lateralis (Fig. 72, d). Ventral 
border with the cleidomastoid (Fig. 73, d) and one head of the 
levator scapule ventralis (Fig. 72, c’). 
Action.—Flexes the head laterally. 
Mm. interspinales and intertransversarii are found in the 
neck region also; they are described with the muscles of the 
back. 
C. MUSCLES OF THE TAIL.—M. extensor caude medialis 
(Fig. 70, ¢).—This is a continuation caudad of the multifidus 
