This obstetrical wax model shows a symmetrical malformation consisting of a cephalothoracopagus monstrosity, in which two symmetrically developed fetuses are joined at the head and thorax. They are in breech presentation, the inferior uterine segment is overdistended, and the umbilical cord is prolapsed. The expulsion stage has been interrupted because the largest part of the fetus is facing the pelvis. The fetus is removable. Of the countless varieties of malformations described in developed and even mature fetuses, double monsters were the most significant in obstetric terms, because of the difficulty of their expulsion during delivery. The smallness and malleability of the two fetal bodies favored their delivery. Nevertheless, forceps and craniotomes were often used.
The model was commissioned by Felice Fontana, who was working on the installation of the Museo di Fisica e Storia Naturale of Florence, from the sculptor Giuseppe Ferrini and his assistant Clemente Susini.