Abstract
This work by Diego Cisneros, a doctor from Madrid, is an example of a 18th-century scientific tract that was published in New Spain in 1817. Although little is known about the author, he received degrees in both Spain and Mexico, was a somewhat pretentious scholar and, despite a familiarity with the works of Copernicus, was a firm believer in classical doctrine (Hippocrates, Galen, Ptolemy). The idea he repeatedly attempts to prove is that all doctors need to understand astrology in order to practice medicine correctly, since celestial influences are determining factors in the development of diseases.