148 THOMPSON YATES LABORATORIES REPORT 
ponding. The list of reflex movements gives many examples. In Monkey, the Vllth 
post-thoracic afferent root provokes flexion of ankle; the corresponding motor root gives 
extension at ankle. The Vlth post-thoracic aflFerent root evokes flexion of hip; the correspond- 
ing motor root gives extension. The Vtli post-thoracic afferent provokes flexion of knee ; the 
corresponding motor, extension at knee. In the Cat, Vlllth post-thoracic afferent provokes flexion 
at hip and dorsal flexion of ankle ; the corresponding motor, extension at hip and plantar flexion 
at ankle. Vllth post-thoracic afferent elicits flexion at hip and knee ; the corresponding motor, 
extension at hip and knee. The Vlth post-thoracic afferent root evokes flexion at knee and hip ; 
the motor, extension. The Vth post-thoracic afferent, flexion at knee ; the corresponding motor, 
extension at knee. In the Monkey, Vllth cervical afferent very frequently evokes flexion at elbow ; 
the Vllth motor root gives, on the contrary, extension of elbow. In the Cat, the same roots also 
give conversely flexion and extension at wrist. The Ilnd cervical afferent root evokes turning of 
the head to the opposite side ; the motor root produces lateral flexion of the head to the same 
side. Sanders-Ezn's phenomenon of the predominance of flexion over extension at knee-joint 
is well illustrated by the case of two monkeys examined in the laboratory almost daily for three 
months after transection in the thoracic region. Hardly once in all that time was homonymous 
extension of the knee elicited from either, although flexion at knee was day after day easily 
elicited. In the Dog I have sometimes failed to find any motor root or set of motor roots which 
gives flexion at the knee, extension always predominating; yet flexion at knee is easily obtained 
in the dog as a reflex from almost any nerve in the whole limb, or by a stimulation of almost any 
part of the skin of the limb, as was noted by Freusberg* in his well-known account of reflexes 
obtainable from the lumbo-sacral cord of the dog. Again : the blow on the tendo patellae which 
evokes the direct (WESTPHAL,t WallerJ) spasm of vastus medialis and crureus§ called 'knee- 
jerk,' fails to elicit a true reflex contraction of those muscles, although frequently evoking a true 
reflex contraction of the hamstring muscles, which, as Lombard|| has shown, succeeds the direct 
extensor spasm. That this hamstring contraction is a true reflex can hardly be doubted, in view 
of the extreme facility with which the hamstrings are reflexly excited, and also in view of a fact 
I have often seen, that the hamstring contraction evoked by the tendon tap occurs even when the 
dissected hamstrings, altogether freed at their lower ends, are lying slack, and when their own 
afferent roots have been cut through. 
Again, the movement evoked by a lower sacral or coccygeal afferent root is often an 
abduction of tail in absolutely the reverse direction of that given by excitation of the correspond- 
ing motor root. 
The list suffices to illustrate the point, a corollary from the previously given rule ; and it 
emphasizes what I have already insisted on, the negation of the view (Os. Polimanti, R. 
Russell) that in the movement produced by direct excitation of a whole motor spinal root we 
reproduce a functional movement of high co-ordination. 
* Pfliiger's 'Archiv,' vol. 9. § Sherrington, 'Joiirn. of Physiol.,' vol. 13, p. 621, 
f- 'Archiv. f. Psych. 11. Nervenkrank.,' vol. 5, p. 803. || 'Journ. of Physiol.,' vol. 10, p. 122. 
J 'Brain,' vol. 3, p. 179 ; 'Journ. of. Physiol.,' vol. 11, p. 384. 
