Figs. 107 and 108. Cutaneous Nerves, according to their Segmental 



(Spinal) Origin. 



The nerves distributed to the upper extremit}' are derived from the 

 segments -- 4th Cervical and 2nd Dorsal inclusive. The distribution is such that 

 the upper segments pass to the outer side and the lower the origin of the nerves, 

 the more internal is their distribution. The thick black lines situated on the 

 Anterior and Posterior aspects of the arm indicate the boundary between the 

 rostral and caudal parts of the limb, the correct continuation of this line on to 

 the forearm and hand is not yet defined. 



WiCHMANN is of opinion that it should continue between the dark-blue 

 and violet areae to the distal end of the ist Metacarpal bone on both the anterior 

 and posterior aspects. 



The segmentary distribution over the attachment of the limb to the trunk 

 differs in front and behind. The posterior divisions of the Cervical Nerves ramify 

 over the posterior aspect: VIII. C and i. D have, as a rule, no posterior division, 

 so that 2. D follows VII. C; again, i. D has not usually even an anterior division, 

 so that the 2nd intercostal nerve foUows directly upon the Supraclavicular branches 

 distributed to the chest. 



The boundaries between the intercostal nerves are diagrammatic in the 

 figure inasmuch as only the middle V.f of ^ colour accurately represents the 

 nerve indicated, the upper and lower thirds being the upper and lower association 

 areae of the nerves. 



In the limb the limitations are much less definite than indicated; moreover 

 there are many variations particularly on the inner side where the red area may 

 be far more extensive and with the brown may pass even as far as the 4th finger. 



The following segments correspond to the different nerves. 



IV. C: — the supra-clavicular nerves. 



V. C (VI. C): — the cutaneous branches of the circumflex. 



(V. C) VI. C, VII. C (VIII. C) : - the cutaneous branches of the Musculo-Spiral. 



VI. C : — the cutaneous branches of the Musculo-Cutaneous. 



On the inner aspect of the limb the Dorsal Nerves enter at the upper 

 part, the Cervical Nerves at the lower. The Intercosto-humeral belongs to the 

 Cervical Plexus if one takes the 2nd Dorsal segment as belonging to this Plexus. 



The Interna] cutaneous is chiefly derived from i. D and VIII. C. The 

 violet band (VII. C) gives the boundary between VI. C and VIII. C as these 

 nerves ramif}' over this area. 



The area of the Median and Ulnar Nerves in the hand are not accurately' 

 defined. The dorsal branch of the Ulnar Nerve chiefly contains VII. C , the 

 palmar branch VII. C (only represented in the figure) and i. D. 



The Palmar branches of the Median Nerve correspond to VI. C and 

 VII. C, the digital branches to VI. C, VII. C, VIIL C (the nearer to the inner 

 side, the lower is the origm of the fibres in the cord). The outer side of the 4th 

 finger ma}- even be partially supplied b)' i. D. 



