204 MUSCLES OF THE BACK. 



bone between the two curved lines, near the occipital spine. A large 

 fasciculus of the complexus is so distinct from the principal mass of 

 the muscle as to have led to its description as a separate muscle under 

 the name of biventer cervicis. This appellation is not inappropriate 

 for the muscle consists of a central tendon, with two fleshy bellies. 

 The complexus is crossed in the upper part of the neck by a tendinous 

 intersection. 



Relations. By its superficial surface with the trapezius, splenius, 

 trachelo-mastoid, transversalis colli, and longissimus dorsi. By its 

 deep surface with the semi-spinalis dorsi and colli, the recti and obliqui. 

 It is separated from its fellow of the opposite side by the ligamentum 

 nuchae, and from the semi-spinalis colli by the profunda cervicis artery 

 and princeps cervicis branch of the occipital, and by the posterior cer- 

 vical plexus of nerves. 



Fifth Layer. 



Dissection. The muscles of the preceding layer are to be removed 

 by dividing them transversely through the middle, and turning one 

 extremity upwards, the other downwards. In this way the whole of 

 the muscles of the fourth layer may be got rid of, and the remaining 

 muscles of the spine brought into a state to be examined. 



The SEMI-SPINALES MUSCLES are connected with the transverse 

 and spinous processes of the vertebrae, spanning one half of the verte- 

 bral column ; hence their name semi-spinales. 



The SEMI-SPINALIS DORSI arises from the transverse processes of 

 the six lower dorsal vertebrae, and is inserted into the spinous pro- 

 cesses of the four upper dorsal, and two lower cervical vertebrae. 



The SEMI-SPINALIS COLLI arises from the transverse processes of 

 the four upper dorsal vertebrae, and is inserted into the spinous pro- 

 cesses of the four upper cervical vertebrae, commencing with the axis. 



Relations. By their superficial surface the semi-spinales are in rela- 

 tion from below upwards with the spinalis dorsi, longissimus dorsi, com- 

 plexus, splenius, with the profunda cervicis and princeps cervicis artery, 

 and posterior cervical plexus of nerves. By their deep surface with the 

 multifidus spinae muscle. 



Occipital Group. This group of small muscles is intended for the 

 varied movements of the cranium on the atlas, and the atlas on the 

 axis. They are extremely pretty in appearance. 



The RECTUS POSTICUS MAJOR arises from the spinous process of 

 the axis, and is inserted into the inferior curved line of the occipital 

 bone. 



The RECTUS POSTICUS MINOR arises from the spinous tubercle of 

 the atlas, and is inserted into the rough surface on the occipital bone, 

 beneath the inferior curved line. 



The RECTUS LATERALIS is extended between the transverse pro- 

 cess of the atlas and the occipital bone ; it arises from the transverse 



