THIS communication deals with a glucose effect on the permeability of cell membranes to sugar molecules as studied by the intensity of respiration when leaves of Artocarpus Integrifolia were injected with varying concentrations of glucose solution. The investigation developed as a very interesting by-product of other investigations on respiration. Though the important role of carbohydrates in the physiology of the living cell has been recognised for a very long time, our knowledge concerning the direct penetration of living cells by carbohydrate molecules is only recent. Scarcely anything is known, however, about the effect of sugar on the permeability changes of cell membranes to diffusion of sugar molecules. Curiously, the direct evidence for an effect of this kind of sugars on the permeability of cell membranes is obtained from an investigation which had primarily nothing to do with the problem.