Page:Mind (New Series) Volume 12.djvu/494

 480 w. MCDOUGALL: being filled by the opaque cards ; the two cards overlapped and the distance between the two coloured fields could be adjusted by sliding the one card behind the other. The white borders aid in maintaining perfect coincidence of the two coloured fields. The one square was orange, the other blue. Each observation lasted during one complete rotation of the drum, i.e., 118 seconds, and each was repeated with the cards transposed, so that in the one observation orange was presented to the left eye and blue to the right eye, and then in a second observation, under otherwise similar con- ditions, blue was presented to the left eye and orange to the right eye. The results of these parallel observations are presented side by side in the following table. The muscles for accommodation of lens and pupil of the left eye were completely paralysed through previous application of atro- pine, the right eye was normal. In the pairs of observations I., II. and III. the two fields were at such a distance apart that they appeared combined when the visual axes were approximately parallel. I. Passive. a. 6. Left eye. . UO = 36" 17 B = 20" Bight eye. . 16B = 37" 29 O = 45" N = 45" N = 53" II. Holding B. a. b. Left eye. . 26 O = 17" 17 B = 31" Right eye. . 27 B = 52" 29 = 29" N = 49" N = 58" III. Holding 0. a. b. Left eye. . 22 = 45" 14 B = 11" Eight eye. . 20B=16" 29 = 59" N = 57" N = 48" In the case of the following pair of observations the two- fields were 20 mm. nearer together than in preceding cases, so that their binocular combination involved a moderate degree of convergence of the two eyes. IV. Passive. a. b. Left eye. . 12 = 8" 9 B = 9" Right eye. . 19 B = 32" 24 = 26" N = 78" N = 83" In this table ' Passive ' means that throughout the obser- vation my attitude was as far as possible that of a passive