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In reference to a theorem proved by Sugawara and Kanazawa together with recent studies of asymptotic behaviour by Omnes, the subtration in the dispersion relations of Gi(t) and Ti,(t) is discussed. The contributions to the r,(t) and Fπ,(0 by the "far away" singularities are accounted for more carefully; the results so obtained seem to agree pretty well with both the electric and magnetic isotopic vector form factors; the Ti,(t) satisfies the requirement proposed by Vick from the analysis of π-N scattering data. Our calculation also shows that the total isotopic vector charge and magnetic moment are mainly due to the 2π intermediate state contribution; it is very probable that there exist no core point charge and magnetic moment at all.