The Minute Anatomy of the Brachial Plexus. 433 



cutaneous was seven times noted separately, in all of which it came 

 from the 8th aloue. That part of the muscle which arises below the 

 musculo- spiral groove, commonly called the inner head, receives the 

 ulnar collateral nerve on its inner part, and another branch which also 

 serves the anconeus in its outer part. These two nerves were in 

 six instances derived from the 8th only, in three from both 7th and 

 8th, in two from the 7th only, and in one from the 7th with the 

 addition of a fibre from the 6th. In eleven cases where the supply 

 of the outer head of the triceps was traced separately, it came from 

 the 8th alone once only, from both 7th and 8th twice, from the 7th 

 alone twice, from the 6th and 7th once, and from the 6th alone in 

 five cases. In fourteen instances the nerves to the separate heads 

 were not traced apart, but the whole muscle together with the 

 internal cutaneous branch was in all supplied below the 6th. In 

 three more the inner and outer heads were taken together, and in 

 these also the supply was from the 7th and 8th. 



The 6th therefore only entered the triceps in five out of twenty- 

 eight cases, and it is to be noted that in No. 19, the only case where 

 the 6th entered the inner head, it wholly supplied the outer. 



The next branches given off are the two external cutaneous. 

 The short branch was noticed in fourteen cases. Eight times it was 

 shown to come from the 6th alone, once from both 5th and 6th, and 

 in the remaining five from the first two roots, the 5th not being- 

 excluded. The long branch sprang from the 6th five times, in two of 

 which the 5th was not excluded, from both 6th and 7th once, from 

 the 7th thrice, from the 7th and 8th four times,* and from the 8th 

 thrice. 



The nerve then supplies the brachialis anticus. The branch, or 

 branches, going to this muscle, which are very small, were isolated 

 eight times. They were traced each time to the 6th, but in three 

 cases the 5th was not excluded. 



The branch to the supinator longus was traced twenty-two times, 

 always to the 6th, but in twelve cases the 5th was not excluded. 



The extensor carpi radialis longior was served twelve times by the 

 6th alone (in eight the 5th was not excluded), once by both the 6th 

 and the lower nerves, and ten times by the lower part of the musculo- 

 spiral, in four of which the 7th alone was traced to it, in five 

 the 7th and 8th were not separated, and in one both were found 

 supplying it. 



The brevior was supplied by the 6th six times, in four of which 

 the 5th was not excluded, once by both the 6th and the lower nerves,, 

 and nine times by the lower nerves alone, in four of which the 7th 

 was the agent, and in one both 7th and 8th. 



* In one case formed by the 7th and 8th the twig from the 7th ran nearer the 

 radial border than that from the 8th. 



