The rate of diffusion of gases through animal tissues, with some remarks on the coefficient of invasion

THE rate at which gases and especially oxygen will diffuse through tissues has, so far as I am aware, never been systematically investigated and practicallv never been investigated at all, though a knowledge of the gas diffusion is obviously essential for the solution of one of the problems of the physiology of to-day: the supply of oxygen to the cells. The brilliant work of B a rcroft and his collaborators has made it comparatively easy to obtain a quantitative idea of the average oxygen tension in the capillaries and has furnished many of the necessary data concerning the call for oxygen of the tissues, but in order to make out how this call can be met it is necessary (1) to measure and calculate the average distances which the oxygen molecules have to travel from the capillaries until they enter into chemical combination, and (2) to know the rates at which they travel, that is the diffusion coefficients for oxygen in the different tissues. The present paper is intended to supply the second of these desiderata for certain tissues. The diffusion of gases through animal tissues must take place in essentiallv the same way as their diffusion through fluids or colloidal membranes. The gases are dissolved in the tissue fluids and diffuse in a liquid state. The laws governing the diffusion of gases through water and watery solutions have been worked out by Exner(i), who found that the rates of diffusion for different gases in the same fluid are proportional to the absorption coefficients of the gases in the fluid and inversely proportional to the square roots of their molecular weights. Exner could onlv measure relative diffusion rates for different gases. Stefan(2) measured directly the rate of diffusion of carbon dioxide. Hufn er (3) devised a method for measuring directly the diffusion rates