  On the basis of the model of the current flow through a single fibre, changes
in the electric charge density over the myocardium are described. With the use
of relevant analytic formulae, supported with numerical calculations, the
distribution and time dependencies of electric potentials on the surface of the
thorax have been determined. The results obtained are compared with empirical
data. A strong correlation between the theoretical predictions and the
experimental data has been obtained. The model in question permits examination
of instantaneous potentials resulting from electrical activation of particular
segments of the cardiac muscle.
