Replacement of diffusive by convective gas transport in the developing hen's egg.

Comparison of diffusive and convective transport equations for O2, CO2 or H2O in the gas-phase shows that for the same gas flux (ml . day-1) and the same pressure difference (Torr) one can substitute an effective air ventilation, VA (ml . day-1), for a given diffusive conductance, G, (ml . day-1. Torr-1). The theoretical relation is: VA = (RT) . G. Thus air ventilation of 865 ml . day-1 (BTPS) is required for each unit of G. This relation was tested in the developing chick embryo (days 15 to 19) by continuously ventilating the air space beneath the shell while the egg was maintained at 37.8 degrees C in air or submerged. During this exposure normal development, oxygen uptake, and gas tensions were maintained, verifying the theoretical prediction.