PRE VERTEBRAL REGION. 73 



transverse process of the atlas, and is inserted into the 

 rough surface of the occipital bone external to its condyle. 



The SCALENUS ANTICUS MUSCLE arises from the anterior 

 tubercles of the transverse processes of the third, fourth, 

 flh, and sixth cervical vertebrae, and is inserted into a 

 ubercle on the upper surface of the first rib ; this tubercle 



important to notice, since it may be felt by the finger in 



arching for the subclavian artery when that vessel is to 



tied, and the artery lies directly behind this insertion of 

 muscle. The vertebral origin, it will be observed,- 

 corresponds with that of the rectus anticus major muscle, 

 of which it may in some sort be considered the continua- 

 tion. 



The SCALENUS MEDIUS MUSCLE arises from the posterior 

 tubercles of the transverse processes of all the cervical 

 vertebrae, except the first, and is inserted by two fleshy 

 bellies into the first and second ribs, the one inserted into 

 the second being smaller than that into the first rib ; the 

 attachment to the second rib is often described as a separate 

 muscle, under the name of scalenus posticus. 



Between the anterior tubercles of the transverse pro- 

 cesses of the cervical vertebrae, are the anterior pairs of 

 the inter-transversales muscles, the first pair being between 

 the atlas and axis, and the last between the last cervical 

 and first dorsal vertebrae. The lower anterior inter-trans- 

 versalis muscle is often wanting. Between the pairs, ex- 

 cept in the first two spaces, the anterior primary branch of 

 the cervical nerves makes its exit ; beneath . the posterior 

 muscle the posterior primary branch of the same nerve 

 emerges. 



The anterior division of the first spinal or sub-occipital 

 nerve, is given off from the common trunk while the latter 

 lies upon the posterior arch of the atlas ; it then curves 

 downward in front of the transverse process of the atlas, 

 and forms a loop of communication with an ascending 

 branch of the second cervical nerve; it supplies the rectus 

 lateralis and rectus anticus minor, and communicates with 

 the pneumogastric, hypoglossal, and sympathetic nerves. 



The anterior division of the second cervical nerve passes 

 over the lamina of the axis, is directed forward, outside the 

 vertebral artery, and beneath the inter-tracsversalis muscle 

 of the first space, to join the cervical plexus. 



The vertebral artery, already described at p. 58, may be 

 further examined, by removing the inter-transversales mus- 



