376 A MANUAL OF ANATOMY. 



Cervicalis Ascendens. (External column.) 



Origin. From the angles of the five upper ribs. 



Insertion. Into the posterior tubercles of the transverse 

 processes of the fourth, fifth, and sixth cervical vertebrae. 



Nerve Supply. The external posterior branches of the 

 cervical nerves. 



Action of External Column. To extend and flex later- 

 ally the cervical, dorsal, and lumbar regions of the spine. 

 To draw the ribs downward and act to aid expiration. 



DISSECTION. 



Remove the above muscles to expose the deeper layers which occupy the 

 space between the spines and tips of the vertebrae and transverse processes of 

 the vertebrae. 



The muscles comprising the two last layers will not be given here, as their 

 study and dissection is more theoretical than practical. 



The sixth layer is composed of the complexus (see page 

 132), semispinalis dorsi, semispinalis colli, multifidus spinae, 

 and rotatores spinae. The seventh layer is formed of the 

 interspinales and the intertransversales. 



For the suboccipital muscles see Head and Neck, page 1 34. 



The Posterior Branches of the Spinal Nerves. 



For the cervical nerves see page 1 29. 



The dorsal, lumbar, and sacral : These are found coming 

 through the muscles filling the spinal gutter in two sets, an 

 external and internal set. They supply the overlying mus- 

 cles and terminate in the integument. 



Not much time need be spent in dissecting out these 

 nerves ; they can be examined as the dissection proceeds. 



DISSECTION. 



Continue to remove the integument from the forearm, hand, and fingers, as 

 before directed. See page 360. 



The arrangement of the superficial veins should be noted. There is a great 

 amount of variation in their formation. The usual plan is given below. 



