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THE NERVOUS SYSTEM 



areas of the limbs are arranged in serial correspondence with the spinal nerves, the 

 middle nerves of each limb series passing to the distal extremity while the higher and 

 lower nerves are limited to the proximal regions. Thprburn's observations, which 

 differ from Head's, are, especially as regards the upper limb, in close conformity with 

 the results obtained by Sherrington's experiments on monkeys. 



THE CUTANEOUS AREAS OF THE UPPER LIMB 



The skin over the upper third of the deltoid muscle is supplied by the posterior 

 supra-clavicular (supra-acromial) and middle supra-clavicular (supra-clavicular) 

 nerves, which are branches of the cervical plexus containing fibres of the third and 

 fourth cervical nerves, and that over the lower two-thirds by the axillary (circumflex) 

 nerve which conveys fibres of the fifth and sixth cervical nerves (fig. 710). 



The skin over the front of the upper arm is supplied externally by the axillary 

 (circumflex) nerve above, and below by the superior branch of the dorsal antibra- 

 chial cutaneous, the external cutaneous branch of the radial (musculo-spiral) nerve. 

 The former contains filaments of both the fifth and sixth cervical nerves, and the 

 latter filaments of the sixth alone. The skin of the inner side of the upper arm is 

 supplied by the medial antibrachial cutaneous (internal cutaneous) nerve with 



FIG. 711. DIAGRAM OF THE CUTANEOUS AREAS OF THE UPPER EXTREMITY. 

 (Modified from Head.) 



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fibres of the eighth cervical and first thoracic nerves, and by the medial brachial 

 cutaneous (lesser internal cutaneous) and intercosto-brachial (intercosto-humeral) 

 nerves which are derived from the first and second thoracic nerves. The back of 

 the upper arm is supplied, externally, by the fifth and sixth cervical nerves through 

 the axillary (circumflex) nerve and by the dorsal antibrachial cutaneous; the middle 

 portion, by the eighth cervical nerve through the posterior brachial cutaneous, 

 the internal cutaneous branch of the radial (musculo-spiral) nerve; and the inner 

 portion by the first and second thoracic nerves through the medial brachial cutaneous 

 (lesser internal cutaneous) nerve, and the intercosto-brachial (intercosto-humeral) 

 nerve (fig. 710). 



The front of the forearm is divided into two areas, an outer, which is supplied 

 by the fifth, sixth, and possibly the seventh cervical nerves, through the musculo- 

 cutaneous branch of the brachial plexus, and an inner, supplied by the eighth 

 cervical and first thoracic nerve through the medial antibrachial cutaneous 

 (internal cutaneous) nerve. On the back of the forearm there are three areas: (1) an 

 outer, supplied by fibres of the fifth and sixth cervical nerves through the mus- 

 culo-cutaneous nerve; (2) a middle, which receives fibres of the sixth, seventh, 

 and eighth cervical nerves through the lower branch of the dorsal antibrachial cu- 

 taneous of the radial (inferior external cutaneous branch of the musculo-spiral nerve), 

 and (3) an inner which receives the eighth cervical and first thoracic nerves through 

 the medial antibrachial cutaneous (fig. 710). 



