Each of the different transport mechanisms to be considered , i.e. transport by hydrodynamic flow and transport by diffusion , must operate in the same way for transport of heat and for transport of mass , since the differential equations are identical in the two cases. Therefore the extent to which mass transport is enhanced in bolus flow , as compared to Poiseuille flow , may be deduced from a study of heat transport. Thermal measurements are technically much simpler since temperatures are more easily measured than , for example , O2 concentration . for this reason the present study was carried out on a thermal analogue . In order to apply the results to the capillary circulation , it was then necessary to take into account not only the difference in scale , but also the difference in diffusion coefficients (thermal vs. gaseous)