438 



Mr. W. P, Herringham. 



coraco-brachialis continuing down the post-axial border, are served by 

 the 7th * 



Of the muscles running to the upper end of the forearm, the biceps 

 and brachialis anticus are supplied from the 5th and 6th ; the triceps 

 by the 7th and 8th, and it is remarkable that of the three heads of 

 the triceps the outer, which is nearest to the pre-axial border, is the 

 highest in the series. 



At this point the 5th ends. 



Of the muscles arising about the outer condyle, the highest in rank 

 are the two supinators inserted into the radius, next the extensors of 

 the carpus going to the radial side of the hand. Of those coming 

 from the internal condyle, the two outermost, nearest, that is, to the 

 radius, are supplied by the 6th. The innermost, the flexor carpi 

 ulnaris, is supplied by the 8th and 9th (and at this point the 9th first 

 begins to share in the system) ; the flexor sublimis, between the two, 

 is supplied by the 7th and the lower nerves. None of the deep 

 muscles are served by the 6th, and the 7th seldom runs to them. 

 They are as a rule innervated by the lowest of the series. 



Passing to the hand, the superficial muscles on the outer side are 

 supplied by the 6th, the superficial on the inner side by the 8th, the 

 deep muscles being again supplied by the lowest of the nerves supply- 

 ing the hand, namely, the 8th. 



It is remarkable and unexpected that the 8th and not the 9th should 

 be the nerve going to the muscles of the hand. The explanation I 

 would suggest is that the motor part of the 9th is rather an auxiliary 

 nerve than an integral part of the plexus. The extremely small 

 part which it often plays in the ulnar, and the fact that in two 

 cases none of its fibres could be traced thither at all, confirm this 

 view. 



The cutaneous supply of the limb exemplifies still more clearly 

 the first of the rules laid down for the motor system. Over the 

 deltoid runs the descending branch from the 3rd and 4th, below this 

 comes the circumflex from the 5th, or from the 5th and 6th. The 

 branch of the 5th in the musculo-cutaneous, and the short external 

 cutaneous of the musculo-spiral given by the 6th, supply the skin over 

 the outer condyle and head of the radius. Down to the end of the 

 radius it is served by the musculo-cutaneous, either from the 6th 

 alone, or as in one case by the 5th and 6th ; the thumb is supplied by 

 the 6th in the median and radial. 



On the inner side, the highest part, the skin of the axilla, is served 

 by the 10th, the area below this by the junction of the 9th and 10th 

 (the intercosto-humeral with the nerve of Wrisberg), next by the 9th 



* The deltoid, which would also exemplify the law, is omitted. I consider it 

 uniform with the pectoralis major, not truly part of the long muscles of the limb. 



