154 
THOMPSON YATES LABORATORIES REPORT 
Rule of Uniformity of Response despite Spatial Variety of Provocation 
From the above we are led almost as a corollary to a rule of uniformity of response despite 
spatial variety of provocation, for it is obvious that excitation of any one of a large number of 
afferent channels will evoke approximately the same movement in reflex response. 
Examples: — The digital nerves of foot or hand separately excited evoke the same movement, 
although their segmental value and root composition is severally very different, varying from 5 + 6 to 7 + 6 
in the foot, and from 6 + 7 ( + 8) to i + 8 in the hand. The same result occurs when, instead of the 
nerve-trunks, various points of the skin of hand and foot are excited. 
Jgdhi : — If, in the Cat, the cord is divided at Xlth thoracic level, and the afferent roots of Ilird, 
IVth, \'th, Vlth, V'lIIth, IXth, and Xth right post-thoracic nerves cut, the field of aesthesia of the 
right limb is that of the Vllth post-thoracic nerve. The reflex movements elicitable from this field is then 
studied with special regard to difference of movement in result of difference of locality of stimulation. The 
field of remaining jesthesia includes whole of foot, the outer and (less) the inner aspect of the ankle, the 
outer aspect of the lower half of the leg, and the calf nearly up to the popliteal space. A slight pinch of 
the skin at any point within the whole of this area elicits a contraction in the hamstring muscles and in the 
median half of the gracilis ; this contraction is accompanied by flexion of the ankle, and by some spreading 
of the toes when the pinch is applied to the dorsum pedis or planta, especially the pad. The contraction 
in the hamstring muscles is chiefly in the inner hamstrings when the inner side of the foot, chiefly in outer 
hamstrings when the outer side of the foot, is the place of provocation. A deep reflex, e.g., a pinch of the 
tibialis anticus tendons, elicits the same contraction of medial half of gracilis as do the skin reflexes. A 
crossed reflex, exciting the crossed quadriceps extensor cruris, was obtainable from the whole of the skin area. 
Again : — If the afferent roots of the limb-region of the Dog are split up into a series of filaments, 
twenty-five in number, all fairly equal in size (I have prepared the filaments as follows : — IXth post-thoracic, 
one filament ; Vlllth post-thoracic, four filaments ; Vllth post-thoracic, six filaments ; Vlth post-thoracic, 
five filaments ; Vth post-thoracic, three filaments ; IVth post-thoracic, two filaments ; Ilird post-thoracic, 
two filaments ; Ilnd post-thoracic, one filament), excitation of each of these, except the first and sometimes 
the twenty-fifth, usually readily evokes flexion of knee, and from the uppermost twenty flexion of hip can 
usually be obtained. Sometimes each of the whole series of twenty-five will evoke flexion of knee. 
Again : — From the cervical afferent roots of the Monkey, by individual excitation in descending 
series, contraction of supinator longus muscle is obtainable from each in succession from Ilird cervical to 
Vlllth cervical, though not usually inclusive of the latter. 
The rule which these examples illustrate may be briefly termed the rule of spatial 
monotony. It seems important enough to warrant the subjoined furtfier illustrations, obtained 
from animals in which there was some depression of spinal reflex activity. The results on the 
Cat should be compared with the movements obtained from the motor roots of that animal by 
Langley* and myself.t 
Cat : — Transection above 1st cervical ; the movements provoked by exciting the separate 
afferent roots were — 
right IXth post-thoracic root , , flexion of right knee. 
Vlllth 
Vllth 
Vlth 
Vth 
IVth 
Ilird 
Ilnd 
knee, hip, ankle, and toes. 
knee, hip, ankle, and toes. 
knee, hip, ankle, and toes. 
knee, hip. 
hip, knee. 
hip. 
hip. 
* ' Journ. of Physiol.,' vol. i 2, p. 366. 
t 'Journ. of Physiol.,' vol. 13, p. 6zi. 
