This report presents a model-independent method of assessing contributions to the light scattering from individual organelles in single intact cells. We first measure the 3D index map of a living cell, and then modify the map in such a way so as to eliminate contrast due to a particular intracellular organelle. By calculating and comparing the light scattering distributions calculated from the original and modified index maps using the Rytov approximation, we extract the light scattering contribution from the particular organelle of interest. The relative contributions of the nucleus and nucleolus to the scattering of the entire cell are thus determined, and the applicability of the homogeneous spherical model to non-spherical and heterogeneous organelles in forward scattering is evaluated.