1881.] The Brachial and Lumbo- Sacral Plexuses. 



17 



in the subscapulars, nmsculo-spiral, and median — possibly also the 

 external anterior thoracic to the pectoralis major. 



Sixth Cervical. — The upper arm is adducted and retracted, the fore- 

 arm extended and pronated, the wrist flexed, and the palm of the hand 

 brought against the pubes. 



This movement generally occurs quickly, and the palm of the hand 

 is brought smartly backwards towards the middle line. 



It seems to be the action which, if the hands were the fixed point, 

 would raise the body upon a trapeze or branch. 



We noted the contraction of the pectoralis, the latissimus dorsi, 

 triceps, and flexors of carpus. The pronators were also evidently in 

 action, though not visible. 



These muscles imply stimulation of the external anterior thoracic, 

 long subscapular, and branches of the musculo- spiral and median 

 nerve. 



Fifth Cervical. — The upper arm is raised upwards and iniuards, the 

 forearm flexed and supinated, the wrist and. basal phalanges extended. 

 The fingers assume a claw position with their distal phalanges bent. — 

 The result of this action is to bring the hand up to the mouth. 

 Among the muscles in action we specially noted the deltoid, its 

 clavicular portion more particularly, the serratus magnus, the flexors 

 of the forearm — biceps, brachialis anticus, and supinator longus. 

 Also the extensors of the wrist and basal phalanges. 



These muscles imply stimulation of nerves conveyed by the circum- 

 flex, musculo-cutaneous, and musculo-spiral, and apparently also the 

 median (long flexors of fingers). 



Fourth Cervical. — The shoulder and tipper arm are raised upivards and 

 backwards, the forearm flexed and supinated (and the wrist extended). — 

 The action here is in other respects similar to that of the fifth cervical, 

 except in the raising the arm upwards and backwards. The muscles 

 we observed in action were the deltoid, the rhomboid, the supra- and 

 infra-spinatus muscles, the flexors of the forearm and extensors of the 

 wrist, though occasionally the last were not observed. 



During stimulation of this root respiration ceases from spasm of tlie 

 diaphragm. 



The action described implies stimulation of fibres conveyed by the 

 rhomboid, supra- scapular, circumflex, musculo-cutaneous, and muscmo- 

 spiral nerves, and also of the phrenic. 



We would likewise note a fact which may require further investiga- 

 tion, viz., that in one case in which we specially directed attention to the 

 pupil, during stimulation of the motor roots from the first dorsal up 

 to the fourth cervical, no action on the pupil was observed, though 

 the usual movements of the limb occurred. This is a fact which is of 

 importance in reference to the question of a cilio-spinal centre in the 

 lower cervical region of the cord. 



VOL. XXXII. c 



