The restricted energy loss of electrons, positrons, protons, and pions passing through nuclear emulsions has been measured by observation of the variation in blob and grain density as a function of γ=1(1-β2)12. All measurements were made in small areas (7 cm2) of two Ilford K-5 emulsion pellicles. A careful examination of the variation of blob density with track depth was made in both pellicles. The results of our measurements on the relativistic rise (5<γ<36) as well as on the Fermi plateau (γ>100) are in agreement with the predictions of the Sternheimer formula using a mean ionization potential I of 434 eV and a cutoff energy W0 of 6-10 keV. An upper limit of 1% is placed on radiative corrections of the type predicted by Tsytovitch. Correction for the finite number of developable grains traversed by the primary produced a best fit with W0=6 keV, in excellent agreement with the maximum energy of a δ ray that comes to rest within the working volume of blob counting.