Francisco Hernández de Toledo
Hernández was among the first wave of Spanish Renaissance physicians practicing according to the revived principles formulated by Hippocrates, Galen and Avicenna. Hernández studied medicine and botany at the University of Alcalá and may have traveled between cities in Spain as was common among physicians seeking to make a name for themselves. Moving from Seville with his wife and children, Hernández served briefly in the Hospital y Monasterio de Guadalupe and then at the Hospital Mendoza in Toledo, where he gained prominence for his studies of medicinal botany and publication of a Castilian translation of a work on natural history by Pliny the Elder. In 1567 Hernández became a personal physician to King Philip II.
Scientific Expedition to the New World
In 1570 Hernández was ordered to embark on the first scientific mission in the New World, a study of the region's medicinal plants. Accompanied by his son Juan, he traveled for 7 years collecting and classifying specimens, interviewing the indigenous people through translators and conducting medical studies in Mexico. He was assisted by three indigenous painters (baptized, Antón, Baltazar Elías and Pedro Vázquez respectively), who prepared illustrations. 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. Hernandez described the gruesome symptoms of the epidemic (referred to as cocoliztli, Nahuatl for "pest") with clinical accuracy.
Parts of Francisco Hernández' extensive descriptions of his findings were published in a translated collection entitled Plantas y Animales de la Nueva Espana, y sus virtudes por Francisco Hernandez, y de Latin en Romance por Fr. Francisco Ximenez (Mexico, 1615) also cited as Cuatro libros de la naturaleza y virtudes de las plantas y animales que están recibidos en uso de medicina en la Nueva España published by Francisco Jiménez.
A heavily redacted compendium in the original Latin was later published as Rerum medicarum Novae Hispaniae thesaurus (Rome, 1628) by collector, Federico Cesi.
Another impression was put out by Johannes Schreck and Fabio Colonna as Nova plantarum, animalium et mineralium mexicanorum historia a Francisco Hernández in indis primum compilata, de inde a Nardo Antonio Reccho in volumen digesta (Rome: Vital Mascardi, 1648).
Some of Hernández' original manuscripts are housed in the library of the Escorial, but many were lost in the fire of July 17, 1671. A new compilation by physician Casimiro Gómez Ortega, based on additional material found in the Colegio Imperial de los Jesuitas de Madrid was entitled Francisci Hernandi, medici atque historici Philippi II, hispan et indiar. Regis, et totius novi orbis archiatri. Opera, cum edita, tum medita, ad autobiographi fidem et jusu regio. (1790).
- Alfredo de Micheli-Serra. Médicos y medicina en la Nueva España del Siglo XVI. Gaceta Médica de México. May/June 2001, vol.137, no.3 (accessed 16 November 2005 available on the World Wide Web: . ISSN 0016-3813
- Fundació Catalunya-Amèrica Sant Jeroni de la Murtra revista RE (Edición castellano), "El preguntador" Época 5. número 45. pp. 57–60. julio de 1999  accessed November 16, 2005.
- Acuna-Soto, Rodolfo; David W. Stahle, Malcolm K. Cleaveland, Matthew D. Therrell. (Octubre-Diciembre 2002). "Megadrought and Megadeath in 16th Century Mexico" (PDF). Revista Biomédica (Mérida: Universidad Autónoma de Yucatán) 13 (4): 282–289. ISSN 0188-493X. Archived from the original on September 21, 2009. Retrieved September 7, 2012. Lay summary – Geographical Review, Vol. 96, Issue 3, pages 502–505 (July 2006). "Summary. The native population collapse in 16th century Mexico was a demographic catastrophe with one of the highest death rates in history. Recently developed tree-ring evidence has allowed the levels of precipitation to be reconstructed for north central Mexico, adding to the growing body of epidemiologic evidence and indicating that the 1545 and 1576 epidemics of cocoliztli (Nahuatl for "pest") were indigenous hemorrhagic fevers transmitted by rodent hosts and aggravated by extreme drought conditions."