 Along the way, he also interviewed the indigenous people through translators and conducting medical studies in Mexico.He was assisted with his illustrations by three indigenous painters - Baptized Antón, Baltazar Elías and Pedro Vázquez.During the colonial-period population decline of the Aztecs in 1576, Hernández performed autopsies in the Hospital Real de San José de los Naturales in collaboration with surgeon Alonso López de Hinojosos and physician Juan de la Fuente.