If the semen of one part come in greater quantity from the male than from the female, this part will resemble more closely the father; if, however, it comes more from the female, the part will rather resemble the mother.

If it be true that the semen comes from both parents, then it is impossible for the whole body to resemble either the mother or the father, or neither the one nor the other in anything, but necessarily the child will resemble both the one and the other in something.

The child will most resemble the one who contributes most to the formation of the parts." Such was the Hippocratic theory of generation and heredity, and it was ingeniously used to explain the hereditary nature of certain diseases and malformations.

For instance, in speaking of the sacred disease (epilepsy), Hippocrates says: "Its origin is hereditary, like that of other diseases; for if a phlegmatic person be born of a phlegmatic, and a bilious of a bilious, and a phthisical of a phthisical, and one having spleen disease of another having disease of the spleen, what is to hinder it from happening that where the father and mother were subject to this disease certain of their offspring should be so affected also?
As the semen comes from all parts of the body, healthy particles will come from healthy parts, and unhealthy from unhealthy parts." According to Pare, Damascene saw a girl with long hair like a bear, whose mother had constantly before her a picture of the hairy St.John.
Pare also appends an illustration showing the supposed resemblance to a bear.

Jonston quotes a case of Heliodorus; it was an Ethiopian, who by the effect of the imagination produced a white child.