Studies from the Biological Laboratory of the Johns Hopkins University, Baltimore, vol. iv., Nos. 5 and 6.—No. 5 contains:—Some observations on the effect of light on the production of carbon dioxide gas by frogs, by H. Newell Martin and Julius Friedenwald. The influence exercised by light on the metabolisms of the animal body has been recognized for the last fifty years. Following up the researches of Moleschott, the authors experimentally proved that, in frogs deprived of their cerebral hemispheres, a greater quantity of carbon dioxide is given off in the light than in the dark; that, therefore, the influence of light in producing greater oxidations in normal frogs is simply reflex, and not due to greater bodily activity brought about by psychical conditions dependent on the light; that the cerebral hemispheres do not take any direct part in regulating the oxidations of the frog's body; and that this reflex action of the light, though mainly effected through the eyes, is produced partly also through the skin.—On the comparative physiological effects of certain members of the ethylic alcohol series (CH4O to C3H12O) on the isolated mammalian heart, by John C. Hemmeter. —On the ventricular epithelium of the frog's brain, by A. C. Wightman. The author concludes that the epithelial layer of the frog's brain and spinal cord forms a continuous lining to the central nervous system. It is everywhere a single layer thick. The epithelium of the ventricles forms a central zone of cells, about which the brain-cells are concentrically arranged. The cells of the epithelium and of the brain are connected by processes which extend from the tips of the former. The epithelial layer consists of cells of several varieties—the columnar, the spindle, and intermediate forms; all are ciliated.—On the temperature limits of the vitality of the mammalian heart, by H. Newell Martin and E. C. Applegarth.