small molecules such as glucose and lactate can rapidly diffuse throughout the interstitium, as illustrated in Figures 3 A & B. The rate constant (kapp) for molecular diffusion between two points (separated by ?? cm) in space is given by:Thus for D-glucose (D = 7 ?? 10???6 cm2.s???1 at 37??C), Dapp = 4.4 ?? 10???6 cm2.s???1 and kapp for diffusion across 25 ?? 10???4 cm (the average midpoint betwee