THE MUSCLES OF THE NECK AND BACK 183 



region they are single bands between the transverse process 

 and behind the cervical nerves. 



Short Muscles of Rotation Vertebrae and Occiput. Five on 

 each side; two rise from the axis and three from the atlas. 

 (1) M. rectus capitis posticus major. Origin, spine of the axis, 

 upper border; insertion, into and below the middle third of the 

 inferior curved line of the occiput. (2) M. obliquus capitis 

 inferior, strongest of these muscles. Origin, upper and pos- 

 terior part of the arch of the axis (Henle) ; insertion, back part 

 of the transverse process of the atlas. (3) M. rectus capitis 

 posticus minor. Origin, posterior tubercle of the atlas; insertion, 

 into and beneath the inner third of the inferior curved line 

 of the occiput, covered partly by the major muscle. (4) M. 

 obliquus capitis superior. Origin, upper surface of transverse 

 process of the atlas; insertion, impression between the outer 

 parts of the occipital curved lines. (5) M. rectus capitis lateralis. 

 Origin, anterior surface of the apex of the transverse proces 

 of the atlas; passes nearly straight up to the jugular process 

 of the occiput. 



The two oblique muscles, with the rectus capitis posticus 

 major, form the suboccipital triangle, in which are found the 

 vertebral artery and the posterior primary branch of the sub- 

 occipital nerve (Quain). 



The extensor coccygeus is a slender fasciculus, occasionally 

 present, which extends over the lower part of the posterior 

 surface of the sacrum and coccyx. It arises by tendinous 

 fibers from the last bone of the sacrum or first piece of the 

 coccyx, and passes downward to be inserted into the lower 

 part of the coccyx. It is a rudiment of the extensor muscle 

 of the caudal vertebra? of the lower animals (Gray.) 



Nerves. All of the foregoing muscles of the neck and back 

 are supplied by posterior primary branches of the spinal nerve. 



Actions. The longitudinal muscles extend the back with 

 a force of 200 to 400 pounds; some of the lower muscles may 

 depress the ribs and aid in forced expiration; some of the upper, 

 if fixed above, may act in forced inspiration. The muscles 

 of one side produce lateral flexion of the spinal column. The 

 complexus and transversospinalis rotate the head and spine 

 to the opposite side. The rectus minor and superior oblique 

 chiefly extend the head; the rectus major and inferior oblique 

 rotate the atlas and skull on the axis; the major also extends 



