THOMPSON YATES LABORATORIES REPORT 
tremulant or quite steady, and of longer duration. Many of them when quite vigorous are 
nevertheless clonic ; for instance, the abduction of thighs with flexion of toes obtainable in the 
hind-limb by exciting the fore-paw is in the Cat nearly always clonic. Some are long, i.e., persist 
for nearly a minute — exhibiting steady contraction all along with a final access (p. 134). This I 
have seen especially in flexion of knee and in flexion of elbow. Finally, as the reflexes become 
more active, 'march' develops, taking courses as above described. A feature frequent in 
thoroughly active spinal reflexes is alternating discharge of antagonistic muscles, especially, perhaps, 
at ankle and at wrist. The alternations may recur many times over. The reflex contractions of 
one of the alternating groups are usually much shorter than of the other : thus, at ankle and 
wrist the plantar flexion and the dorsal extension are shorter, sharper than the return movements. 
This I saw in reflexes moving the ankle of Frog, and recorded in a former paper.* WuNDT-f- and 
FickJ have noted that some reflex contractions seem from duration and other characters to be 
simple twitches. In the 'tail-wagging reflex' the alternate opposed contractions seem to be about 
equal in all respects one to the other. 
Inhibition in Spinal Reflexes. 
It has been shown by Goltz and Freusberg§ that in the Dog spinal reflexes can be 
inhibited by appropriately timed strong excitations of the skin. Thus, pinching of the tail stops 
the 'beating-time' reflex of the Dog. They found, too, that a cord tied round a leg may, in the 
Dog as in the Frog, make all reflexes inelicitable from the limb for a time. Nipping the tail 
sometimes succeeds in interrupting micturition in the Monkey — spinal transection in mid-thoracic 
region. The local homonymous leg reflex will inhibit the crossed (p, 163). 
My own observations lead me to believe that inhihito-motor spinal reflexes occur quite 
habitually and concurrently with many of the excito-motor described in this paper. In graphic 
records of the reflex limb movements of the Frog the sudden and absolute relaxation of the 
muscles of one group at the very moment (to a .05") of the onset of contraction in the antergetic 
groupll suggests this. Again, after spinal transection in Dog or Cat, the flexion reflex being 
obtained in the idio-lateral limb by pressing the foot, if while that limb is drawn up by the reflex 
the other foot is squeezed, not only is the squeezed leg drawn up, but the limb previously flexed 
is, very usually, let down : relaxation of the flexors occurring concurrently with contraction of the 
extensors. This co-ordination I term reciprocal innervation. 
That when the flexors of knee and hip are reflexly thrown into action the extensors are 
inhibited, seems proved by the impossibility of obtaining the crossed reflex in the extensors when 
the foot of the crossed side is pinched. 
Again, on two occasions, once in Cat and once in Macacus, the leg lying at the time in a 
state of rigidity due to tonic spasm of the extensor muscles of hip and knee, gentle excitation of 
the central end of a twig of the internal saphenous nerve at the ankle at once produced relaxation 
* ' Journ. of Physiol.,' vol. 13, p. 621, 1892. 
t' Mechanik. cler Nerven u. Nervencentren,' Stuttgardt, 1876. 
\ Pfliiger's ' Archiv,' vol, 3, p. 326. 
§ Pfliiger's ' Archiv,' vols. 8 and 9. 
II Sherrington, 'Journ. of Physiol.,' vol. 13, 
p. 722, Plate 23, 1892. 
