LONDON. Royal Society, May 7.—M. D. Waller: (1.) The measurement of actinic erythema produced by ultraviolet radiation with special reference to the latent time. Consistent results regarding the biological action of ultra-violet radiation, as measured by the resulting skin erythema, can be obtained provided certain precautions are taken. The latent time of erythema, which may vary from about one to seven hours, according to the length of exposure, provides the most accurate and simple way of estimating the effect of ultra-violet radiation on the skin, and it is easily measured. When it is desired to get the maximum contrasts due to differing conditions of radiation, exposures should be chosen which will lie on the steep part of the curve, corresponding to rapid variations of the latent time with exposure and to slight erythemas which will differ even visually one from another more than will deep erythemas.—(2.) The relation between energy doses of ultra-violet radiation and actinic erythema produced. Particular attention was paid to the question of how the intensity of the radiation decreases with the distance from the source. The intensities were varied over wide limits (200: 1) corresponding to distances varying from 40 cm. to 5-5 m. The effect of a given dose of the weak intensity is just as great as that of the most powerful intensity used, and it is concluded that the production of erythema follows the Bunsen-Roscoe law for a photo-chemical action, that is, the time factor is unity.—J. W. Tudor Thomas: On the return of sensitiveness in corneal grafts in rabbits. In a series of experiments on corneal grafting, some of the grafts became sensitive and others did not. The results of 29 experiments are analysed. Some of the grafts were central in position in the cornea, others marginal. Some remained or became clear; others became more or less opaque, while one exhibited a central clear area. The establishment of an afferent nerve supply to a corneal graft depends upon a precedent or concurrent growth of blood vessels in that graft. It does not seem to be necessary that the blood vessels should accompany or take the same path as the afferent nerves that grow in from the surrounding tissue.—G. E. Briggs and A. H. K. Petrie: Respiration as a factor in the ionic equilibria between plant tissues and external solutions. The conductivity of water containing slices of tissue from carrot root rises at first and then falls to a steady value, which is maintained as long as the tissue is alive. The rate of evolution of carbon dioxide by the system follows a similar course to that of the conductivity. Theoretical consideration shows that variations in the rate of production of carbon dioxide by the tissue will be accompanied by similar changes in the concentration of hydrogen ions in the tissue. This will result in changes in the degree of ionisation of indiffusible substances, such as proteins, with consequent changes in the distribution of diffusible ions, such as K and Cl, between the tissue and the external solution. The final result of this chain of events will be a parallelism between rate of production of carbon dioxide and conductivity of external solution.—McKeen Cattell, T. P. Feng, W. Hartree, A. V. Hill, and J. L. Parkinson: Recovery heat in muscular contraction without lactic acid formation. Muscles poisoned with iodo-acetic acid contract without producing lactic acid. Functional recovery in oxygen after stimulation can be demonstrated under certain conditions in such muscles. The persistence of this ‘recovery’ heat suggests that one effect of iodo-acetic acid is to interfere with the mechanism by which energy released in oxidation can be employed in driving the endothermic reactions necessary for functional recovery; it does not interfere with oxidation as such. Normal muscles stimulated to extreme exhaustion have a ‘recovery’ heat only about one quarter of its usual value in relation to the initial heat. Possibly in normal muscles pushed to extreme exhaustion, as in muscles poisoned with iodo-acetic acid, one reason of incomplete recovery is that phosphate set free by the breakdown of creatine-phosphoric acid is ‘side-tracked’ as hexose phosphoric ester and so cannot be recombined with creatine. A. G. R. Whitehouse: Further investigation of sweating and sweat. For a given rise in body temperature, sweating is facilitated by the performance of muscular work when compared with sweating produced by the same rise in body temperature with the subject at rest. Some product of muscular metabolism is responsible for this, though the connexion may be a less direct one. The performance of a moderate amount of work would seem to be accompanied by little rise in the chlorine concentration of the sweat, although a marked increase with time, indicative of fatigue of the sweat-glands, is evident when the subject is at rest and the sweating is simply due to the wet-bulb temperature of the surrounding air. A progressive decrease in the proportion of organic matter to ash is observed as the sweating continues. The chlorine concentration, and also the ratio of chlorine to potassium in the sweat, is found to vary for different individuals.—R. Snow: Experiments on growth and inhibition (2). In decapitated pea seedlings, which have produced two equal shoots springing from the axils of the cotyledons, if one of the shoots is deprived of its leaves until only those of 1 mm. or less remain, it is rapidly arrested in growth and finally killed. This effect must be due to inhibition coming from the other shoot. The influence coming from developing leaves kills (directly or indirectly) those shoots or parts of shoots that are not in the line between developing leaves and roots and in which it travels towards the apex, and this fact also suggests that it is of a polar nature.