Note 25 — Chapter II

Such a skin affection, known as icthyosis, xerosis or xeroderma, is usually due to heredity. Davenport says it "is especially apt to be found in families in which consanguineous marriages occur and this fact, together with the pedigrees [which he studied], suggests that it is due to the absence of some factor that controls the process of cornification of the skin. On this hypothesis a normal person who belongs to an affected family may marry into a normal family with impunity, but cousin marriages are to be avoided." See Davenport, C. B., Heredity in Relation to Eugenics, p. 134. New York, 1911.