Role of diffusion in gas exchange of the avian egg

The pore system of the avian eggshell provides a unique exchange surface for the transport of gases. The dimensions of the microscopic pores do not change with time, and gas transport through them is essentially limited to diffusion. According to Fick's law of diffusion, eggshell conductance of a given gas will vary directly with the diffusion coefficient of the gas. This principle is illustrated by monitoring changes in air space CO2 in metabolizing eggs subjected to changes in barometric pressure or to substitutions of He and SF6 for N2 in the ambient atmosphere.