154 



ATLAS AND TEXT-BOOK OF HUMAN ANATOMY. 



two vertebrae before inserting into the roots of the spinous processes, their fibers having a 

 course parallel to that of the multifidus. 



All of the long muscles of the back are supplied by the posterior divisions of the spinal nerves (cervical, thoracic, 

 lumbar, and sacral). 



The majority of the long muscles of the back have the same functions. If the muscles of the two sides act together, 

 they hold the trunk upright, extend the vertebral column and the head, and bend the head and vertebral column back- 

 ward. During unilateral action they bend or rotate the vertebral column toward the contracting side. The strongest 

 action upon the head is exerted by the two semispinals capitis; when they act together, they pull the head backward, 

 but when they act singly they rotate the head so that the face is drawn toward the opposite side, and consequently in 

 the opposite direction to that in which it is turned by the splenius capitis. 



THE SHORT MUSCLES OF THE BACK. 



The short muscles of the back are divided into two groups : those which are found through- 

 out the entire flexible vertebral column and those which are situated between the axis and the 



Intertransversarii mediates c—— 



/ Intertransversarii lalerales 



Interspinales / 



Fig. 244. — Diagram of the lumbar interspinals and intertransversarii. 



atlas. The first group is composed of two further subdivisions: the iiijj ^Jihwks, between the 

 spinous processes of the vertebrae; and the intertransversaiii. between the transverse processes. 

 The second group is also designated as the short muscles of the neck. 



The interspinales (Figs. 241, 243, and 244) are small muscles which are well developed 

 only in the cervical region and may be entirely wanting throughout the thoracic vertebral column. 

 They are connected with the interspinous ligaments and pass from the spinous process of one 



