Exercitatio anatomica de motv cordis et sangvinis in animalibvs
Sumptibus F. Fitzeri, Francofvrti, 1628
Harvey discovered the true nature of how blood circulates in the human body and presented it for the first time in this small book. He demonstrated how blood flowed in a circulatory pattern with the heart acting as a pump. Prior to Harvey, the general belief was that blood ebbed and flowed within the body in a sort of tidal action.