520 



DISSECTION OF THE BACK. 



Cutaneous 

 nerves how 

 derived. 



In the neck 



Second 



and third 

 nerves. 



The trape- 

 zius. 



Dissection. 



Divide 

 trape/ius. 



Clean spinal 



accessory 



nerve 



and parts in 



posterior 



triangle. 



Ligamentum 

 nuchse. 



CUTANEOUS NERVES. The tegumentary nerves of the back are 

 derived from the posterior primary branches of the spinal nerves, 

 which divide amongst the deep muscles into two pieces, inner and 

 outer. Arteries accompany the greater number of the nerves, 

 bifurcate like them, and furnish cutaneous offsets. 



CERVICAL NERVES (fig. 2, p. 4). In the neck the nerves are 

 derived from the inner of the two branches into which the posterior 

 trunks divide : they perforate the trapezius, and supply the neck and 

 the back of the head. They are four in number, and come from the 

 second, third, fourth, and fifth nerves. 



The branch of the second nerve is named GREAT OCCIPITAL, and 

 accompanies the occipital artery to the back of the head, where it 

 has already been seen (p. 506). 



The branch of the third cervical nerve supplies a transverse offset 

 to the neck, and then ascends to the lower part of the head, where 

 it is distributed near the middle line, internal to the great occipital 

 nerve, with which it usually communicates. 



The position and attachments of the TRAPEZIUS in the neck should 

 be carefully made out and the student may read the description of 

 the muscles on pages 4 to 6. 



Dissection. On the second day the trapezius and latissimus dorsi 

 muscles are divided longitudinally and the parts thrown outwards 

 and inwards. The trapezius is divided about two inches from the 

 middle line, but before dividing it the student should make out the 

 spinal accessory nerve in the posterior triangle of the neck as it passes 

 downwards and outwards to the under surface of the muscle ; the 

 nerve being looked for at the posterior border of the sterno-rnastoid 

 about the junction of the upper with its middle third. Parallel 

 with, but below, the spinal accessory, and communicating with it 

 beneath the trapezius, will be found branches of the third and 

 fourth cervical nerves. 



The branches of the superficial cervical artery to the under surface 

 of the trapezius will also be cleaned and after the reflection of the 

 inner part of the muscle the dissector should clean the splenius, and 

 the upper part of the levator anguli scapulae, and define the things 

 beneath the clavicle, viz., the posterior belly of the omo-hyoid 

 muscle (fig. 210, p. 576) with the suprascapular nerve and vessels, 

 as well as the transverse cervical vessels, and the small nerves 

 to the levator anguli scapulae and rhomboid muscles. If the 

 trapezius be detached along the middle line, the ligameiitum 

 nuchae, from which it takes origin, will be brought into view. 



The LIGAMENTUM NUCH^: is a narrow fibrous band which extends 

 from the spinous process of the seventh cervical vertebra to the 

 external occipital protuberance. From its deep surface a thin 

 layer of fibres, which forms a median partition between the 

 muscles of the two sides of the neck, is sent forwards to be 

 attached to the external occipital crest and to the other cervical 

 spines. 



Dissection. On the third day after the latissimus dorsi has been 

 divided, the dissector of the head and neck is to examine the 



