Fig. 105 and io6. Areae of distribution of Cutaneous Nerves 

 of Upper Extremity, (right). 



Outlines of Figs, after Fau's Atlas. Colours correspond to those employed for 

 the spinal segineiiis in the subsequent figures. 



Unfortunately the areae of distribution of the nerves of the hmb and 

 their variations have not been completely worked out, as in the case of the Head 

 and the Trunk by Frohse and Zander. For practical purposes the diagrams 

 will probabl}' suffice. 



The upper part of the shoulder (green) is supplied from the Cervical 

 Nerves. The front of the chest is supplied by the Anterior Branches of the 

 Intercostal Nerves (yellow) , the back by the Posterior Branches. The Lateral 

 Branches suppl\^ the Axilla and even the upper part of the inner aspect of the arm. 



When the arm is supinated the anterior boundary between adjacent areae 

 of distribution extends down the middle of the anterior aspect of the arm to the 

 tip of the 4th finger. But the posterior boundar}' line runs down the middle of 

 the arm to the 3rd finger. 



The following points should be observed : — 



The upper part of the shoulder is supplied b}- the Supra -Clavicular 

 and Supra-Acromial Branches of the Cervical Plexus. 



The lower part of the shoulder by the Circumflex. 



Below this level the Musculo-Spiral supplies the skin on the outer aspect 

 of the arm corresponding to the area supplied b\- the Internal Cutaneous (red) 

 and Lesser Internal Cutaneous Nerves on the inner aspect. (A further internal 

 branch from the Musculo-Spiral Nerve — Gegenbaur — may assist in com- 

 pleting tlie supply of this region.) 



On the inner part of the anterior (flexor) surface of the forearm is to 

 be found the Internal Cutaneous Nerve, the dorsal branch of which supplies the 

 inner aspect of the posterior (extensor) surface; on the outer aspect of the back 

 of the forearm the chief nerve is the Radial, only a very small area being 

 supplied by the Musculo-cutaneous Nerve. 



In the palm of the hand the cutaneous distribution of the Median (violet) 

 and Ulnar (brown) is divided by a line which runs along the axis of the 4th 

 finger. Special branches from the Median and Ulnar Nerves supply smaU areae 

 in the upper part of the Palm. On the outer side a small area of the Thenar 

 eminence is supplied by the Radial Nerve. 



The Dorsum of the hand is supplied equally by Radial and Ulnar Nerves, 

 but where these become wanting in the case of the 2nd, 3rd and 4th fingers, 

 their deficiency is made up by the Median Nerve. (Cf. Fig. 106.) 



