122 
THOMPSON YATES LABORATORIES REPORT 
The scheme represents, by horizontal lines, the longitudinal localization in the Ape's brachial 
spinal segments of the motor nerve-cell groups for the simpler functional muscle-groups of the limb. 
X ZK ym viT VI v iv 
Protraction of shoulder . , I I 
Jbdiiction of shoulder . ____ 
Outward rotation of shoulder . , 
Flexion of elhoiv .... 
Supination of forearm . . . _________ 
Adduction of shoulder . . . , 
Radial abduction at wrist . . „___„_____=_ 
Extension of wrist .... ___„_____«_______ 
Iniuard rotation of shoulder . ________-_^_ 
Extension of elbow .... ___.___—. .i___- 
Extension of fingers .... i 
Flexion of wrist | 
Retraction of shoulder . . \ , 
Pronation of forearm . . . | 
Flexion of fingers .... . . | _— __ 
Interosseous flexion of fingers . ■ 
Adduction of fingers. . . ^_________^— . 
Abduction of fingers . . | 
Certain simple movements of the limb are not seen at all on the stimulation of individual 
motor roots : e.g., in many monkeys no root gives extension of the poUex, and in some monkeys 
no root gives extension of the wrist, and I have met with an individual in which no root evoked 
extension of the fingers. In the Dog often no motor root dorsoflexes ankle or flexes the knee. 
In the Monkey, again, no root gives abduction of the pollex or little finger. If the muscles 
producing one movement at a certain joint predominate in one root, it does not follow those pro- 
ducing the opposite movement of the joint need predominate in another. Nor is the supposition 
borne out that muscles whose action predominates in one root always predominate in that root ; 
thus, in the Cat, the Vlth sub-thoracic root occasionally gives flexion of knee, though usually 
extension. In the Dog the Vllth sub-thoracic root generally produces extension of the knee, 
and generally spreading of the toes, but occasionally flexion of knee, and occasionally flexion of 
the toes. The Vlth cervical root of Macacus usually produces extension of the wrist, but some- 
times flexion ; the Ilnd thoracic of Macacus usually produces flexion of the wrist, but occasionally 
only flexion of the fingers and thumb. 
