. Diseases of metabolism and of the blood, animal parasites, toxicology. Constitutional diseases; Metabolism; Blood; Medical parasitology; Poisons. HEMOPHILIA 419 operative in another remarkable afEection—night-llindness (hemeralopia). Although this disease, strictly considered, is not within the realm of our theme, nevertheless it is so interesting that this slight digression is permis- sible. Our knowledge regarding the etiology of night-blindness, in so far as heredity is concerned, is limited to the following points: First, that hemeral- opia, if it is hereditary, attacks more men than wom
. Diseases of metabolism and of the blood, animal parasites, toxicology. Constitutional diseases; Metabolism; Blood; Medical parasitology; Poisons. HEMOPHILIA 419 operative in another remarkable afEection—night-llindness (hemeralopia). Although this disease, strictly considered, is not within the realm of our theme, nevertheless it is so interesting that this slight digression is permis- sible. Our knowledge regarding the etiology of night-blindness, in so far as heredity is concerned, is limited to the following points: First, that hemeral- opia, if it is hereditary, attacks more men than women, and that the disease is frequently met with when the parents are blood relatives; further, that the disease has been observed in several children of the same family, and has been followed through several generations, from four to six. In literature we find that where the disease has appeared in successive generations partly sons and partly daughters were attacked (Sedan, Eecueil d'ophthalm., 1885: Two fam-. FiG. 24.—Genealogical Teee op a Family showing Daltonism. (After Horner.) Daltonists are shaded. ilies: in the first there are only 12 members, 5 females and 7 males, that were affected, and in the second family, of 9 that were affected, 5 females and i males. Savenzy (Irish Hospital Gazette, 1872) reports a family of 5 brothers and 5 sisters, of whom 2 brothers and 3 sisters had night-blindness); or the disease may attack only the sons in a generation, and in such cases we occasionally find the type of heredity which is characteristic of hemophilia and of Daltonism. We owe to E. Ammann, eye specialist in Winterthur, the Imowledge of the fact that night-blindness is transmitted according to the same laws as hemo- philia and Daltonism. Ammann reports the family tree of a hemeralopic fam- ily from which the law of heredity may be determined with absolute certainty (Fig. 25). At the same time the observation that night-blindness and myopia are often combined receives an
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