176 THOMPSON YATES LABORATORIES REPORT 
the reflex movement at the hip seems negligeable, for I have often remarked the reaction at the 
hip to be unaltered, whether the ankle w^ere flexed or extended, at the time of excitation. 
In some dogs, when the spinal transection has been made at the hinder end of the thoracic 
region, stimulation of the skin of the limb evokes the usual primary flexion at hip and knee 
wherever the locus of the stimulus, except it be in the upper three-fourths of the front of the thigh. 
Applied in this latter region, the stimulus, if the limb be midway between extension and flexion, 
not unfrequently evokes reflex extension at hip and knee ; it does not evoke extension if the initial 
posture of the limb be extension ; but if the limb be, at the time of application of the stimulus, 
well flexed at hip and knee, reflex extension, instead of reflex flexion, becomes the rule. 
In the spinal frog, as in the spinal dog, flexion at hip and knee is the regular reflex response 
of the musculature of the homonymous hind-limb to skin stimuli applied at any part of the surface 
of that limb. This being true when the initial posture of the limb is, as when pendent, one of 
extension at hip, knee, and ankle, a difference becomes evident when the initial posture is one of 
flexion at those joints. In the latter case excitation of the skin within a small gluteal and pubic 
area, lateral and somewhat ventral to the cloacal orifice causes, extremely frequently, not flexion at 
hip, but extension at that joint. Stimuli (mechanical and chemical) to that area, which evoke 
flexion at the hip-joint when the initial posture of the limb involves extension at that joint, evoke, 
when the initial posture is flexion, reflex extension at the joint. 
These instances seem to indicate distinctly that the direction which a spinal reflex 
movement, elicited by stimuli similar in all respects, including 'locality,' may take, is in part 
determined by the posture already obtaining in the limb at the time of the application of the 
stimulus. 
The reaction described above for the spinal frog holds good after previous removal of all 
the skin from both hind-limbs, with the exception of the small gluteal piece necessary for 
application of the skin stimulus. It would appear, therefore, that the influence of the posture of 
the limb upon the spinal condition and reaction is not traceable to the nerves of the cutaneous 
sense-organs of the limbs. There still remain the afferent nerves subserving muscular sense, and 
connected with the sense-organs in muscles, tendons, and joints. These, as is well known, are 
largely aflfected by the various postures of the limb, even by such postures as are passively induced. 
