LONDON. Royal Society, November 1.—E. G. T. Liddell and Sir Charles Sherrington: A comparison between certain features of the spinal flexor reflex and of the decerebrate extensor reflex respectively. Comparison of the tetani of the knee flexor, evolved by motor nerve stimulation and by reflex excitation, shows somewhat close resemblance between them. A constant difference is the presence of after-discharge in the latter. A further difference frequently found is, the myograph records being isometric for both, a steeper ascent and sharper ascent-plateau turn for the reflex. The reflex tetanus, like the “motor-nerve “tetanus, appears to engage from its very beginning the full quota of the motoneurones that it will at any time under its further continuance engage. The steeper ascent in the reflex is due to after-discharge setting in early, so that some of the motoneurones activated by the reflex cannot respond to the immediately succeeding series of stimuli. Intensity and not duration in the external stimulus is therefore the sole arbiter of the intensity of the reflex tetanus. Similar comparison of the crossed “reflex of the knee extensor with the “motor-rterve” tetani of that muscle shows that the reflex tetanus develops much the more slowly, and that the ratio between the tension developed by the reflex contraction to a single shock and that to a serial stimulus is much less than under “motor-nerve “stimulation. The reflex at its outset appears to activate only a small fraction of the quota of motoneurones that it will gradually bring into activity.—J. Barcroft and H. Barcroft: The blood pigment of Arenicola. The blood pigment of Arenicola Marina differs from the haemoglobin of human blood in certain respects. The a band of the oxy-haemoglobin is situated 18 A.U. nearer the violet and the a band of the carbon monoxide haemoglobin is situated n A.U. nearer the violet than the corresponding human band. The dissociation curves show a greater affinity for both oxygen and carbon monoxide than those of human blood. The affinity for carbon monoxide is about 70 times that for oxygen, as compared with 250 in man and 140 in the mouse. The possibility of a relationship between the position of the bands and the affinity of the pigment for gas is discussed. The main unloading of oxygen from the pigment of Arenicola would appear to be between i and 3 mm. pressure. The mean oxygen capacity of the haemoglobin per gram of Arenicola is about 0.01–0.013 c-c-A comparison between the oxygen capacity of the pigment and the total oxygen consumption of the worm shows that the pigment holds sufficient oxygen to supply the animal for 1–2 hours, and probably acts as a reserve to tide it over the period at low-water when its hole is closed.—T. Deighton: The basal metabolism of a growing pig. The basal metabolism of a pig has been measured at various ages from seventy-five days upwards, and it has been shown that in the pig, as in human beings, the metabolism per unit area is greatest in mid-youth. This increase of metabolism in youth seems to be directly ascribable to growth. Metabolism after the ingestion of food reaches a maximum after five hours and then declines. The rationing of pigs for maintenance and growth is discussed, and it is concluded that the curve of rationing for growth and maintenance, without fattening, cannot possibly be a two-thirds power curve.