1. The formula originally suggested for the temperature-velocity relationship in simple biological processes has been found to be identical with Slotte's formula for the temperature-viscosity relationship in various liquids, including water and aqueous solutions. 2. This provides an additional argument in favour of the previously suggested hypothesis that the rate of biological processes is primarily determined by protoplasmic resistance opposing free movement of molecules travelling within living matter, rather than by the rate of chemical change considered by itself. 3. By analogy with its meaning in biology, where it denotes the temperature threshold or specific thermal zero point of a process, the constantα in Slotte's formula can be given the meaning of the temperature threshold of viscous flow, that is the temperature at which a supercooled liquid assumes infinitely high viscosity, when in vitreous state. This conclusion is confirmed mathematically on the basis of the formula itself. 4. The formula also fits data on protoplasmic viscosity, cellular permeability and electric resistance of tissues; equally it fits data on the rate of diffusion in water, membrane dialysis and electric resistance of electrolyte solution. 5. Both the biological and the physico-chemical processes here shown to obey the formula of Slotte, are based upon the movement of hydrated particles in water or along other hydrated particles, and subject to frictional resistance between water molecules, either free or bound by various hydrating forces which may attain a high value in greatly reducing the mobility of water molecules so bound; the frictional resistance presumably varies accordingly. 6. Values ofα in biological rate processes are never lower than −46° C, which is the value ofα for the viscous flow of water, and thus the theoretical value of the solid vitrification temperature of water; they are often higher, as is also the case in the viscous flow of sugar solutions and gelatin solutions; participation of protoplasmic lipids in the determination of a in biological processes is discussed. 7. The formula has also been found valid in certain enzyme reactions in which the equation of Arrhenius gives aμ, varying with temperature; a tentative hypothesis is suggested.