In Sicily, reflections on monsters and on «generative stumbles» first appear in a treatise
from the second half of the sixteenth century, containing one of the first medicalphysiological
descriptions of two-headed births and written in the vernacular by the
famous physiologist and anatomist Giovanni Filippo Ingrassia. Ingrassia's contribution
to the field of teratology is interwoven with his more important and observable activity
in the role of protomedico (chief of the controlling body of all the medical activities
in the Kingdom of Sicily), which required him to make important public decisions
regarding medical care. It seems certain that Ingrassia's scientific treatise cannot be
easily classified along with other teratological descriptions of the second half of the
sixteenth century. Rather, a naturalistic sensitivity emerges that is disengaged from
transcendental presuppositions. Starting with an analysis of this important work by
Ingrassia, this paper then draws comparisons with other teratological treatises.