DISTRIBUTION OF CUTANEOUS BRANCHES 823 



lower and anterior part of the abdominal wall is supplied by the ilio-liypogastric 

 branch of the tirst lumbar nerve. 



The cutaneous supply of the lateral aspect of the body is derived from the lateral 

 branches of the anterior primary divisions of the dorsal ner\'es from tlie second to 

 the eleventh, and the skin over the jjosterior aspect of the l)ody is supplied externally 

 by the posterior divisions of the lateral branches of the dorsal nerves from the 

 third to the eleventh, and internally l>y the posterior i)rimary divisions of the dorsal 

 nerves (fig. 469b), in the upper half by their internal branches and in the lower 

 half i»rincipally by their external branches. 



The Cutaxeous Areas of the VprER Limb 



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

 acromial and supraclavicular branches of the cervical plexus, which contain fila- 

 ments of the third and fourth cervical nerv^es, and that over the lower two-thirds 

 bv the circumflex nerve, which conveys fibres of the fifth and sixth cer^'ical nerves 

 (iig. 469b). 



The skin over the front of the upper ami is supplied externally by the circum- 

 flex nerve above and by the superior external cutaneous branch of the musculo- 

 spiral nerve below; the former contains filaments of both the fifth and sixth cervical 

 nerves, and the latter filaments of the sixth alone. Internally the skin of the upper 

 arm is supplied by the internal cutaneous nen'e with filaments of the eighth cervical 

 and first dorsal nerv^es, and by the lesser internal cutaneous and intercosto-humeral 

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

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

 circumflex nerve, and the external cutaneous branches of the musculo-spiral nerve; 

 mesially by the eighth cervical nerve through the internal cutaneous branch of the 

 musculo-spiral nerve, and internally by the first and second dorsal ner^^es through 

 the lesser internal cutaneous and intercosto-humeral ner^^es (fig. 469). 



The front of the forearm is divided into two areas, an external, which is sup- 

 plied by the fifth and sixth cervical nerves through the musculo-cutaneous branch 

 of the brachial plexus, and an internal, supplied by the eighth cervical and first 

 dorsal nerves through the internal cutaneous nerve. On the back of the forearm 

 there are three areas: an external, supplied by filaments of the fifth and sixth cer- 

 vical nerves through the musculo-cutaneous nen-e; a middle, which receives fila- 

 ments of the sixth, seventh, and eighth cervical nerves through the inferior external 

 cutaneous branch of the musculo-spiral nen'e; and an internal, which receives the 

 eighth cervical and first dorsal ner\-es through the internal cutaneous nerve 

 (fig. 469b). 



The front of the hand is supplied by the sixth, seventh, and eighth cervical 

 nerves and by the first dorsal nerve through the radial branch of the musculo-sjtiral 

 nerve and through the median and ulnar branches of the brachial plexus. The 

 radial nerve supplies the radial side of the thumb by its palmar cutaneous branch; 

 the remainder of the palm and the palmar aspects of the fingers are supplied by 

 the median and ulnar nerves through their palmar cutaneous and digital branches, 

 the median supplving three and a half digits and the ulnar the remaining one and 

 a half (fig. 469b)I 



The dorsal aspect of the hand is supplied by the sixth, seventh, and eighth 

 cervical nerves which reach it through the radial branch of the musculo-spiral 

 nerve and through the median and ulnar nerv'es. The radial nerve supplies the 

 outer part of the dorsum and the outer three and a half digits, except the lower 

 }>arts of the index, middle, and half the ring digits Avhich receive twigs from the 

 median nerve, and the ulnar nerve supplies the ulnar half of the dorsum including 

 the inner one and a half digits. 



The Cutaneous Areas of the Lower Extre:mity 



There are six cutaneous areas in the region of the buttock, three upper and three 

 lower. Of the upper areas the external is supplied by the anterior ])rimary divi- 

 sions of the last dorsal and first lumbar nervt-s through the iliac l)ranches of the 



