MUSCLES OF THE BACK. 205 



ceps cervicis branch of the occipital, and by the posterior cervical 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 vertebra?, spanning one half of the vertebral 

 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 processes 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 processes of 

 the four upper cervical vertebrae, commencing with the axis. 



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

 from below upwards with the spinalis dorsi, longissimus dorsi, complexus, 

 splenius, with the profunda cervicis and princeps cervicis artery, and pos- 

 terior 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 process of 

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

 the atlas, and is inserted into the rough surface of the occipital bone, ex- 

 ternal to the condyle. 



The OBLIQUUS INFERIOR arises from the spinous process of the axis, and 

 passes obliquely outwards to be inserted into the extremity of the trans- 

 verse process of the atlas. 



The OBLIQUUS SUPERIOR arises from the extremity of the transverse pro- 

 cess of the atlas, and passes obliquely inwards to be inserted into the rough 

 surface of the occipital bone, between the curved lines. 



Relations. By their superficial surface the recti and obliqui are in rela- 

 tion with a strong aponeurosis which separates them from the complexus. 

 By their deep surface with the atlas and axis, and their articulations. The 

 rectus posticus major partly covers in the rectus minor. 



The rectus lateralis is in relation by its anterior surface with the internal 

 jugular vein, and by its posterior surface with the vertebral artery. 



Sixth Layer. 



Dissection. The semi-spinales muscles must both be removed to obtain 

 a good view of the multifidus spinae which lies beneath them, and fills up 

 the concavity between the spinous and transverse processes, the whole 

 length of the vertebral column. 

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