The etiology of the disease was a subject of controversy for many years. The early writers ascribed it to sexual excesses, masturbation, alcoholism, heredity, overwork, and various other causes. It was looked upon by some as one of the sequelae of syphilis and was described as a "meta syphilitic" disease by Möbius and a "para syphilitic" disorder by Fournier. It was noted by many as occurring only in the more intellectual and highly developed races and was therefore referred to by Krafft-Ebing as a disease of "syphilization and civilization." Both Bayle and Esquirol mentioned syphilis very casually in their writings. Sandras in 1852 spoke of it as one of the principal causes of general paresis. Its etiological importance was, however, first given serious consideration by Esmarch and Jessen, prominent Danish writers, in 1857. Their views were corroborated by Steenberg in 1860 and by Kjellberg in 1863. The theory of an exclusively specific origin was not generally accepted, however, for many years. Rieger published elaborate statistics in 1886 showing that the incidence of general paresis was sixteen or seventeen times as great in syphilitics as it was in healthy persons. The fact that a definite history of infection was not available in many cases led to considerable doubt. Such eminent authorities as Charcot, Binswanger and Déjerine went so far as to deny that there was any relation between the two diseases. That some uncertainty was warranted by the information at hand is shown by the fact that Kraepelin[169] found a history of syphilis in seventy-eight per cent of his cases, while Sprengeler reported 41.5 per cent, Räcke 57.3 per cent, Torkel fifty-one per cent, Marcus seventy-six per cent, Houghberg 86.9 per cent, and Alzheimer over ninety per cent. This is not at all surprising in view of the statement made by Kraepelin[170] that Hirschl could find a definite history of an initial lesion in only thirty-six per cent of his cases of tertiary syphilis. Hudovernig found that 42.3 per cent of the women suffering from syphilis did not know when they were infected. In discussing this subject in 1897 Krafft-Ebing reported the inoculation of nine paretics with syphilitic virus without the appearance of luetic symptoms in any instance, although reinfections have been mentioned by other authorities.