the model imitates the diffusion and mixing in the plasma
only, and ignores the diffusion into the red cells adjacent to the trapped segment
of plasma. These red cells will act as large "sinks" for 02. The plasma enters a pulmonary
capillary and is abruptly exposed to a higher concentration of oxygen on
its periphery (this is analogous to the point at which the fluid in the model enters
the cooling bath). The resistance to diffusion of 02 through the wall is neglected.
If the plasma undergoes Poiseuille flow, then it is possible to calculate, from equation
24 of the Appendix, the per cent saturation of the plasma at any point along
the capillary. Let us take a capillary diameter of 10 microns, an average velocity
of 0.1 cm/sec., and a diffusion constant for oxygen through plasma of 2 x 10-5
cm2/sec. (cf. reference 12). The average per cent saturation of the plasma in