[The effect of tissue resistance on rheography]

Herewith a formula for the computation of the relative stroke volume in limbs is derived, taking into account the differences between the electrical resistivity of blood and tissues, respectively. In order to properly estimate the influence of this difference in resistivity, the appropriate variables were measured in 20 different persons. Results from these tests indicated that the value for tissue resistivity, on the average, was about 30% above that of the resistivity of blood. Consequently, computations of the stroke volume in limbs that neglect this essential difference in resistivity, contain a systematical error in measurement, amounting to 30%. It is the purpose of this paper to portray a method of considerably reducing this error, without the necessity--in each specific case--to measure blood resistivity.