16 Profs. D. Ferrier and G. F. Yeo. [Mar. 24, 



Tlie resultant actions have been very uniform, though occasionally 

 incomplete, any variations of importance being specially indicated. 



The Brachial Plexus. 



Comprising the roots of the first dorsal, and the eighth to the fourth 

 cervical. 



First Dorsal. — Adduction of tlie thumb, and flexion of the fingers at 

 the metacarpophalangeal joints. — The distal phalanges are slightly ex- 

 tended, and the fingers spread. The transverse diameter of the hand 

 is diminished, and the dorsal aspect rendered more convex. 



The action is that of the intrinsic musoles of the hand. Along with 

 the action in the band there is also contraction of the muscles on the 

 same side of the neck, causing the head to be drawn towards the 

 shoulder. 



In our first two experiments this action was more or less compli- 

 cated by that described under the eighth cervical, due without doubt 

 to imperfect isolation of the irritation. 



Eighth Cervical. — A complex action comprising firm closure of the fist 

 (intrinsic muscles and long flexors of fingers and thumb), pronation 

 and flexion of the wrist (to the ulnar side), extension of the forearm 

 with retraction of the upper arm (long head of the triceps specially in 

 action). The extensor muscles on the back of the forearm generally 

 were specially observed in two instances to be rigid also. 



The action here described may be exactly imitated by pulling some 

 object hanging in front downwards and towards the hip, or by draw- 

 ing a scimitar from heel to point through some object lying in front. 



The muscles involved imply stimulation of nerves conveyed in the 

 ulnar, median, and musculo-spiral. 



The pectoralis major seems also to co-operate in this movement in 

 man, but it was not specially observed in our experiments, though the 

 shoulder was observed to be depressed. This would imply also the 

 internal anterior thoracic, which anatomically is related to the cord 

 formed by the eighth cervical and first dorsal. 



Seventh Cervical. — The upper arm is adducted, rotated inwards and 

 retracted, and the forearm extended so as to bring the dorsum of the 

 hand against the rump, the wrist and fingers flexed (at their second 

 phalanges), so as to bring the tips of the fingers towards the radial 

 side and against the' rump. 



The action here described is the sculptor ani movement, and involves 

 the co-operation of numerous muscles. The teres major, latissimus 

 dorsi, and subscapularis appeared to be in action. The pectoralis major 

 was noted in one instance also. The triceps was also observed to be 

 contracting, and also the long flexors of the fingers. 



These muscles would indicate stimulation of nerve-fibres contained 



