  Using an eikonal structure for the scattering amplitude, Block and Kaidalov
have derived factorization theorems for nucleon-nucleon, $\gamma p$ and
$\gamma\gamma$ scattering at high energies, using only some very general
assumptions. We present here an analysis giving experimental confirmation for
factorization of cross sections, nuclear slope parameters B and $\rho$-values
(ratio of real to imaginary portion of forward scattering amplitudes), showing
that: i) the three factorization theorems hold, ii) the additive quark model
holds to ~1%, and iii) vector dominance holds to better than ~4%.
