156 THE NERVOUS SYSTEM 



rotators of the shoulder, (2) the flexors and supinators of the 

 forearm, and (3) the rhomboids. Sherren's views are sub- 

 stantially in agreement with Kocher's, but Thorburn refers 

 the supra- and the infra-spinatus to the sixth segment. 



Sixth Cervical Segment. To this segment Kocher and 

 Thorburn refer the supply of the muscles which oppose 

 those innervated by the fifth, i.e. (i) the adductors and 

 medial rotators of the shoulder, (2) the extensors and pronators 

 of the forearm, and (3) the serratus anterior. Sherren believes 

 that the sixth segment is not so definitely associated with 

 particular muscle-groups, and he only includes in its supply 

 (i) the clavicular part of the pectoralis major, (2) the pronators, 

 (3) the radial extensors of the wrist, and (4) the serratus 

 anterior. 



Seventh Cervical Segment. Kocher includes both the 

 flexor and the extensor muscles of the wrist, but Thorburn 

 only assigns the flexors to this segment. Sherren only agrees 

 with Kocher with reference to the extensor carpi ulnaris 

 and he includes the triceps, the extensor muscles of the 

 ringers and the sterno-costal portion of the pectoralis major. 

 There is, therefore, very little agreement with regard to the 

 individual muscles supplied by the seventh cervical nerve, 

 probably because it is practically never injured alone, since 

 it is the middle, and longest, of the five main nerves which 

 constitute the brachial plexus. 



Eighth Cervical Segment. The flexor and extensor muscles 

 of the fingers are innervated by the eighth cervical segment, 

 according to Kocher, but Sherren includes the flexors only, 

 and, with them, the flexors of the wrist. Thorburn sub- 

 stantially agrees with the latter. 



First Thoracic Segment. According to practically all the 

 authorities, this segment is responsible for the supply of the 

 small muscles of the hand. In view of the comparative 

 unanimity with regard to the fifth cervical segment, it is not 

 surprising to find the same agreement with regard to the 

 first thoracic, because, on account of their shortness, the 



