225 Trans. Internat. Congress, at Milan, 1881, p. 126.
226 "Nystagmus und seine Aetiologie," A. f. O., xxiv., 4, p. 237 (1878).
227 Klin. Monatsblätter f. Augenheilkunde, vol. xvii., 1879, pp. 419-438 and 461-480.
In some rare cases nystagmus may be produced at will. Raehlmann,228 Lawson,229 Benson,230 all report cases of the voluntary type. In one of those given by Lawson the patient (a gentleman in good health) "first made his eyes steady, and then set both into rapid lateral motion—so rapid that the outline of the cornea was completely lost to view." Zehender231 observed it in a case of a twelve-year-old boy, where he was able to produce it by the instillation of a strong solution of eserine. Charcot states that ordinary nystagmus is a valuable symptom of disseminate sclerosis, and that it is present in about half of these cases, while it is exceptional in locomotor ataxy. "In some patients the look is vague until the eyes are made to fix some object, when the nystagmus develops."
228 Loc. cit.
229 R. L. O. H. Reports, vol. x. p. 203.
230 Ibid., vol. v. p. 343.
231 Klin. Monatsblätter f. Augenheilkunde, vol. xviii., 1879, p. 127 (note).
According to Hammond, in disseminate sclerosis, nystagmus may be the only symptom for the period of a year before other symptoms develop. Moos232 speaks of oscillatory movements of the eyes in Menière's disease, and Schwalbach233 describes them in a case of purulent catarrh of the middle ear where they could be produced either by syringing or by pressure on the mastoid process.