LONDON. Royal Society, June 6.—Sir J. J. Thomson, president, in the chair.—N. B. Dreyer and Prof. C. S. Sherrington: Brevity, frequence of rhythm, and amount of reflex nervous discharge as indicated by reflex contraction. A single momentary stimulus of moderate intensity, e.g. a break-shock, even though not far above threshold value of stimulation, applied to the afferent nerve of a spinal reflex-centre, evokes from that centre not uncommonly a repetitive series of volleys of motor impulses. It tends to do so more as the stimulus, within limits, is increased in intensity, but the state of the reflex-centre at the time is also a decisive factor. The rhythm of repetition of volley-discharges from the spinal reflex-centre was traced, by the ordinary mechanical method, to be of synchronous rate with that of stimulation of the afferent nerve up to a frequence of 55 per sec, and by a mechanical resonance method up to a frequence of 65 per sec. By a “doubling frequency” method it was shown further that the frequence-rate of the reflex discharge has not reached its limit under a stimulation of 75 per sec., but surpasses that degree, though by what amount the method cannot say. The maximal mechanical power of a muscle contracting under spinal reflex action is frequently as great as the maximal which can be evoked from it by direct faradisation of the motor nerve itself.