NYSTAGMUS

(Lat.), n. m. Ni2st(nu6st)-a2g(a3g)'mu3s(mu<s). Gr., vvoray/xa, vv<rrayjiio, vvorafis (from vv<rTa(ei.v, to nod in sleep). Fr., nystagme. Ger., N., Einschlafen im Sitzen (1st def.), Augenzittern (3d def.), Augeniiderzucken (2d def.), Avgenkrampf(3d def.), Augapfelkrampf (3d def.). 1. Extreme drowsine , with occasional relaxation of the cervical muscles and dropping of the head forward. 2. Spasmodic twitching of the eyelids. 3. A rapid lateral or rotatory oscillation of the eyeball, either continuous or intermittent and involuntary or nearly so. [A, 320 (a, 50); F; L, 41 (a, 14); " Brit. Med. Jour.," Nov. 28, 1891, Suppl., p. 176 (a, 50).] Congenital n. See N. adnatus. L,aryngeal n. Of Spencer, rapid rhythmic contractions of the laryngeal muscles synchronous with ocular n. [" Lancet," Oct. 9. 16, 1886. pp. 702, 736 (a. 29).] Miners' n. An acquired form of n. prevalent in certain coal mines; characterized by a rotary oscillation of the eyes a ociated with corresponding apparent oscillations of objects in the field of vision, with giddine , and with headache. The ocular movements are stopped and a sense of comfort is experienced by looking below the horizontal line, while the symptoms are increased by raising the eyes above that line. The prime cause seems to lie in the kind of work performed, in which the gaze is directed upward in a more or le oblique manner, whereby fatigue is induced in the superior rectus and inferior oblique, and also in the internal and external recti muscles, which finally occasions their spasmodic action when brought into employment. [F; "N. Y. Med. Jour.," Aug. 9, 1890, p. 157 (a, 29).] N. adiiatus. Fr., nystagme congenital. Ger., angeborenes Augenzittern. A form of n. occurring at or before birth. Its existence is doubtful. [F.] N. lateral is. ["N. Y. Med. Jour.," Oct. 15, 1887, p. 446 (a, 29).] N. in which the oscillations are in the horizontal meridian. N. inixtus. A combination of n. oscillatprius and n. rotator i us in which the direction of the oscillations is diagonal. [F.] N. oscillator i us. Fr., nystagme oscillant (ou horizontal). Ger., horizontals (or oscillirendes) Augenzittern. A vibrating or oscillatory trembling motion of the eyes in a horizontal direction in which the positive and negative oscillations occur around the axis of the first pair of extrinsic muscles of the eyeball. [F.] N. rotator i us. A circular or rolling motion of the eyes around the visual axis. It is, however, not always or not entirely due to alternate action of the third pair of extrinsic eye muscles, for the rotatory movements may be of the purest kind or they may be united with a lateral or diagonal movement. [F.] Pharyngeal n. Of Spencer, rapid rhythmic contractions of the pharyngeal muscles synchronous with ocular n. [" Lancet," Oct. 9, 16, 1886, pp. 702, 736 (a, 29).] Vertical n. N. in which the oscillations are in the vertical meridian, [a. 29.] [s. 121]