=Other Recessive Conditions in Man.--=If for albinism we substitute certain forms of insanity, hereditary feeble-mindedness (Fig. 28, p. 118), or hereditary epilepsy, all of which apparently follow the same law, we can readily understand how unfit such matings are where both strains are affected. Marriage with similarly defective stock will result in the affection appearing in one-fourth of the progeny, and one-half of them, though apparently normal themselves, will have the capacity for transmitting the imperfection. It is in the existence of such hidden factors that the chief danger in the marriage of cousins, or in fact any consanguineous marriage lies. A few of the various defects which seem to be inherited as recessives when mated with normality are: susceptibility to cancer; _chorea_ (St. Vitus' dance); true dwarfism (all parts proportionately reduced); _Alkaptonuria_ (urine darkens after passage); alcoholism and criminality, where based on mental deficiency; hereditary _hysteria_; _multiple sclerosis_ (diffuse degeneration of nervous tissue); _Friedreich's disease_ (degeneration of upper part of the spinal cord); _Merriere's disease_ (dizziness and roaring in ears); _Thomsen's disease_ (lack of muscular tone); hereditary _ataxia_; possibly the tendency to become hard of hearing with increased age; and possibly, non-resistance to tuberculosis. Of non-pathological conditions in man which are inherited as recessives, apparently either very great or very small intellectual ability are examples. [Illustration: FIG. 28 Chart showing descent of feeble-mindedness as a typical recessive (after Goddard). Squares represent males, circles females; DD, homozygous dominant; DR, heterozygous dominant (i. e. normal although a carrier); RR, pure recessive; N, normal; F, feeble-minded; A, alcoholic.]