[Significance of photometric demonstration of variations in platelet form during aggregation caused by ADP: reality or artefact].

After a short theoretical recall concerning the problem of light scattering, the author presents some experimental studies about the variations of light intensity scattered by platelets during ADP induced aggregation. In contrast to the reports by Born and Michal, experimental demonstration is given, showing that these variations cannot be interpreted in term of shape change, as no theoretical basis supports these phenomea.