STUDIES IN THE REFLEXES OF THE GUINEA‐PIG. I. THE SCRATCH‐REFLEX IN RELATION TO “BROWN‐SÉQUARD'S EPILEPSY.”

Abstract

1. Of 20 guinea‐pigs 14 have survived the operation of resection of a portion of the right great sciatic nerve for a sufficient length of time, and each one of these has exhibited the movements described by Brown‐Séequard as “epilepsy.” None of these have shown “spontaneous” attacks or the condition of “blepharospasm.”2. The movements were evoked by stimulation of a special area of the skin, the adequate stimulus being mechanical pressure. Stimuli consisting of loud sounds, the vibrations of which ranged between 32 and 16,000 per second, of a bright beam of light directed into the eye, and of a warm beam of light directed on to various parts of the special area of skin, were inadequate. Electrical stimuli given in the form of galvanic shocks were inadequate, as also possibly they were when given in the form of rapid double faradic shocks.3. The boundaries of the special zone of skin are larger than those given by Brown‐Séquard. It almost invariably extends further back than the posterior border of the scapula, while it may extend as far forward as the border of the nostril and the edge of the lower lip in the middle line.4. Changes in the condition of this area, and also in that of the lower limb of the side of the lesion, similar to those described by Brown‐Séquard, were observed.5. The movements, which consist of tonic contraction of the muscles of the neck and back, and of clonic movements at the hip‐joint, occur in two stages. In the first of these the movements are confined to the side of the lesion, while in the second they spread to the opposite side.6. The rhythms of the clonic movements observed lay between the limits of 8 and 16 beats per second. The rhythm was slower in the larger animals. It was also slower towards the end of one reflex, and varied when the reflex was evoked from different points in the special area.7. The clonic movements, as studied in graphic tracings, show a marked resemblance in many of their features to the scratch‐reflex observed in the spinal dog.8. They differ from this reflex in the overflow to the opposite side, and in the phenomenon of alternation, as well as in the degree of the tonic factor.9. Once the clonic movements have appeared, they become progressively more extensive up to a certain point as the condition persists. The excitatory value of the maximal stimulus rises.10. The clonic movements may be inhibited by stimulation of the skin on the abdomen of the opposite side by mechanical pressure. In the early stages this inhibition comes on rapidly, but persists for some time after the cessation of the inhibiting stimulus. In the later stages it is established less rapidly, but lasts a shorter time after the stimulus has stopped. Towards the end of a long reflex response the inhibiting stimulus may only affect the clonic movements by slowing the rate of the beats. When the inhibition of the clonic movements is complete, there is also an inhibition of the tonic contraction of the muscles of the side and hip.