The study examines the idea that mothers are more responsible than fathers in generating bad offspring. The author conveys this idea by showing good and bad family lines with the same father but different mothers. Good lines are produced by chaste, docile, and healthy mothers, while bad lines are produced by women who are promiscuous or illegitimate or who are foreigners and "tainted with insanity." The difficulties of the study family are traced from the marriage of a miller to a blood relative and carrier of insanity. The son married a healthy, moral woman, thereby founding one of the family's two good branches. The other son married twice, once to a relative which started the vagabond and criminal family line and once to a better wife which resulted in a good family line. Although the family is outside the impact of environmental factors, it is assumed that in the long run, nature will eliminate the family and its physical weaknesses that become more pronounced with each generation.