AN OBVIOUS feature of infantile progressive muscular atrophy, as first described by Werdnig1 and by Hoffmann2 about fifty years ago, is its familial appearance. This implies that a hereditary factor may play an important part as a cause of the disease. Nevertheless, few attempts have been made to prove this theory and to solve the various genetic problems involved.
Using the sibling method of Weinberg to estimate eventual agreement with mendelian laws, Schimkus3 in 1934 made a calculation on a number of cases collected from earlier publications and concluded from his results that simple recessive inheritance was probable. Schimkus demonstrated that about 25 per cent of all siblings of the primary patients were paralyzed, which was just what he expected to find in case of recessiveness. He did not realize, however, that such ideal figures can be expected only in unselected material. If Schimkus, as I suppose,