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, b). 



Origin from the whole lateral surface of the spine of the 

 axis. The parallel fibres form a thick mass which passes 

 laterad and craniad. 



Inseytio7i 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, a), the complexus (Fig. 69, b), and the 

 obliquus superior (Fig. 71, e). 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, b^, 

 complexus (Fig. 69, <^), and longissimus capitis (Fig. 73, g'). 

 Inner surface with the obliquus inferior (Fig. 71, b'), the wing 

 of the atlas, and the rectus lateralis (Fig. 72, d). Ventral 

 border with the cleidomastoid (Fig. 71, d) and one head of the 

 levator scapulae 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 caudae medialis 

 (Fig. 70, e). — This is a continuation caudad of the multifidus 



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