Farfán went on to perform therapeutic experiments in the Hospital Real de Naturales and serve as protomedic for New Spain, devising one of the earliest medical manuals there.
Farfán is commemorated as a revolutionary doctor and surgeon who was endorsed by the viceroy of New Spain at the time for his ability to offer alternative treatments and medical knowledge accessible to a wide audience, including back in Europe.
With twenty seven-years of experience practicing medicine and surgery,[2] Farfán wrote Tractado breve de anathomía y chirugía, y de algunas enfermedades que más comúnmente suelen haver en esta Nueva España (roughly translating to Brief Treatise on Surgery and the Understanding and Cures of Some of the Illnesses that Commonly Occur in this Land) in 1579,[6] one of the first medical manuals of New Spain.
[1] This edition consists of an alphabetized index of body parts, illnesses, and treatments (especially common ones, such as fevers and dysentery)[7] and sometimes uses his religious authority to substantiate claims.
[8] Aside from the discoveries made by him and his colleagues, Farfán also derived his findings for the book on surgery from Greek, barbarian, and 'modern' scholars; notably, he quotes Aristotle, Hippocrates, and Guy de Chauliac.
[2] As a result, Farfán revised his work, publishing a restructured version of his treatise in 1592, which he dedicated to Luis de Velasco, viceroy of Mexico.
[12] In the second edition, Farfán also challenges doctors of the time, directing them to the last two books in the treatise—anatomy and surgery—and advising them to learn anatomy to avoid making nearly as many mistakes as they were.
[14] He observed the widespread medicinal use of local flora, citing chili peppers, rhubarb, and vanilla as purgatives, alongside warm chocolate as a laxative.
[8] Spanish and Agustinian historian Esteban García asserts that his contemporaries commemorated him as a successful doctor and esteemed surgeon,[3] with distinguished people from all over Mexico attending his consultations.
Farfán is cited in Agustin Verancurt's Teatro Mexicano (1698),[4] a work that notes profound historical, political, and religious events in New Spain.