Pascal, a physician in Plassans for 30 years, has spent his life cataloging and chronicling the lives of his family based on his theories of heredity. Pascal believes that everyone's physical and mental health and development can be classified based on the interplay between innateness (reproduction of characteristics based in difference) and heredity (reproduction based in similarity). Using his own family as a case study, Pascal classifies the 30 descendants of his grandmother Adelaïde Fouque (Tante Dide) based on this model. Pascal has developed a serum he hopes will cure hereditary and nervous diseases (including consumption) and improve if not prolong life.