THE UPPER LIMB 



THE BACK. 



Landmarks. — ^The middle line of the neck presents a median furrow, 

 called the nuchal groove, which lies over the line of the ligamentum 

 nuchae. It is due to the shortness of most of the cervical spinous 

 processes and the prominence at either side, caused principally 

 by the complexus muscle. At the upper end of this groove the 

 strong bifid spine of the axis may be felt by sinking the finger 

 deeply, but the spines of the third, fourth, and fifth cervical vertebrae 

 cannot be detected, as these fall short of the surface so as to allovv 

 of dorsal flexion of the neck. At the lower end of the groove the 

 spine of the seventh cervical or vertebra prominens can readily be 

 felt, and usually also that of the sixth, and succeeding to these are 

 the thoracic and lumbar spines. The spine of the first thoracic 

 vertebra is, as a rule, the most conspicuous of the series. Along the 

 middle line of the thoracic and lumbar regions there is an elongated 

 furrow, called the spinal groove, which is produced by the promi- 

 nence formed by the erector spinae on either side. This groove 

 is best marked in the lower thoracic and upper liunbar regions, and 

 it subsides about the level of the third sacral spine. The outline 

 of the scapula may be made out, unless in very muscular persons. 

 It will be found to extend from the second to the seventh rib, and the 

 spine and acromion process are usually readily felt. The root of 

 the spine is on a level with the third thoracic spine, and the 

 inferior angle coincides with the seventh rib. The crest of the 

 ihmn can be felt at the lower part of the back, its greatest promi- 

 nence being on a level with the fourth lumbar spine. 



Fascia. — ^The superficial fascia is thick, graniilar, and fatty, and 

 in it the cutaneous nerves and vessels are met \vith. The 

 deep fascia is thin and membranous, but firm. It contains no fat, 

 and forms sheaths for the muscles. 



Cutaneous Nerves. — ^These are most readily met with at the 

 level of the deep part of the superficial fascia, and the cutaneous 

 vessels serve as the best guide to them. They are derived from 

 the posterior primary divisions of the spinal nerves, which, with a 

 few exceptions, divide each into an external and internal branch. 



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