Efrén Carlos del Pozo
1907-1979
Mexican physician, scientist and historian who made significant contributions to the fields of physiology, pharmacology, and the history of medicine.
Born on September 11, 1907 in San Luis Potosí, Mexico, Efrén C. del Pozo completed his early studies at the Autonomous University of San Luis Potosí (UASLP), where he also served as a professor and secretary. He went on to earn his medical degree from the National Autonomous University of Mexico (UNAM) in 1936.
Del Pozo pursued advanced studies in physiology at Harvard Medical School from 1940-1943 under the mentorship of physiologist Walter B. Cannon. He also worked as an associate researcher at the National Institute for Medical Research in London in 1947. Upon returning to Mexico, del Pozo held positions at various institutions, including the National Polytechnic Institute (IPN), UNAM, and the Ministry of Health. He was a founding member of the National School of Biological Sciences at IPN and the Mexican Society of Physiological Sciences.
As a researcher, del Pozo made notable contributions to the study of human physiology and pharmacology. He conducted early experiments on the effects of ethnobotanical specimens and traditional Aztec and Mayan medicines, including psychoactive plants. In 1959, American researcher Frank Barron participated in del Pozo’s trials with psilocybin mushrooms in Mexico City, observing their effects on creativity. As Timothy Leary later recalled, it as Barron’s account of this experience that triggered Leary’s own interest in psychedelics.
Del Pozo was also a prominent historian of medicine. He played a key role in the publication of two seminal works of 16th-century Mexican medicine: the 1552 Badianus Manuscript (Libellus de Medicinalibus Indorum Herbis) in 1964, and the complete works of Francisco Hernández, published between 1960 and 1984. These efforts helped preserve and bring attention to the rich history of indigenous medical knowledge in Mexico.
From 1953 to 1961, del Pozo served as Secretary General of UNAM, working alongside rector Nabor Carrillo. In this role, he helped establish the University City campus and modernize the institution's academic and research programs. Del Pozo was also President of the National Academy of Medicine in 1961 and Secretary General of the Union of Latin American Universities.
Throughout his career, del Pozo was known as a dedicated mentor and advocate for scientific research in Mexico. Efrén C. del Pozo passed away on May 14, 1979 in Mexico City.
TAGS: Mexico, physicians, indigenous histories
Del Pozo in 1941, via the Guggenheim Foundation.
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• Del Pozo, "Empiricism and magic in Aztec pharmacology,” in The ethnopharmacologic search for psychoactive drugs, 1967 (1967).
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• Benjamin Breen, Tripping on Utopia: Margaret Mead, the Cold War, and the Troubled Birth of Psychedelic Science (Grand Central, 2024), pg. 184.
“It is evident that Aztec pharmacology at the beginning of the XVI Century had reached an important degree of development: The multiple and well-kept botanical gardens mainly devoted to growing medicinal plants were known and admired not only by Cortes and his soldiers, but by botanists and physicians. Francisco Hernandez, physician to Philip II, collected, described and assayed, numerous plants from those gardens, particularly from the one at Oaxtepec. The discovery of the medicinal properties of those plants was undoubtedly empirical. Contemporaneous chroniclers report that at those botanical
gardens the plants were given free to the patients, under the condition that they would inform about the results...
We know that Aztec pharmacology was based mainly in the use of plants selected by a long empirical testing. Present day laboratory assay has con- firmed the activity of many of them. We are now interested in psycoactive drugs. The Aztecs gave us teonanacatl, peyotl, ololiuhqui, piecetl, toloatzin, already attested in their activity... We have no reason for any doubt on what the 16th century chroniclers tell us about the well trained Aztec physicians with an extensive knowledge of medicinal plants and long experience in diagnosis and treatments.”