. 



180 FIFTH LAYER. 



ing 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 vertebras, 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 vertebras. 



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 vertebras, commencing with the axis. 



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

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

 complexus, splenius, and 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, on 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 pro- 

 cess of the atlas, and is inserted into the rough surface of the occi- 

 pital bone, external 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 transverse process of the atlas. 



The obliquus superior arises from the extremity of the transverse 

 process 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 relation 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 spinns which lies beneath them. 



