482 W. MCDOUGALL : of the dark room, was lit by an evenly grey sky. The centre of this bright square was fixated by both eyes at a distance of 50 cm. The left eye was completely atropinised, the right eye was normal, and an artificial pupil of 2 mm. diameter was worn before either eye. Then with a blue glass before the left eye and a red glass before the right eye a record of the struggle of the blue and red fields was made with the help of the apparatus described above. The resulting figures were : Sum of B periods 21" (left eye) 33" (right eye) and on repeating Sum
Then with the glasses transposed, i.e. with red glass before Sum of B periods = 19" (left eye) R = 26" (right eye). FIG. 7. the left eye and blue glass before the right eye, the figures were : Sum of B periods B and on repeating Sum of R periods B = 8" (left eye) - 37" (right eye) 7" (left eye) 41" (right eye). The asymetrical character of the figures is due to the tendency of the blue field to predominate under equally favourable conditions, but in spite of this the re-enforcement by activity of the intrinsic muscles of the normal eye is very clearly marked. These observations seem to prove in a more direct and conclusive manner than any others with which I am ac- quainted two important points, (1) that the whole cerebro- retinal tract in which colour-sensations are excited is double, i.e., that the tract of either eye is separate and distinct from
