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J. LeConte on Binocular Vision. * 167 
their present organization, were transferred to the sides of our 
heads, with their axes directed straight right and left, and 
therefore making an angle of 180° with each other, «mages of 
objects in the direction of these axes, and —_—- dir ectly roght and 
t, would be moved round 90° each and combined and seen directly 
tn front. This seems an peivlier neti ne but is a necessary 
consequence of the law of corresponding points. The retinal 
images of the two objects are on corresponding points; by the 
law of corresponding points, therefore, they must a seen as 
one. sear else can this ta e place but in fron 
previous papers, raat that “On the mode a representing 
of illusion.”* Those who have read eos papers will remem- 
ber that I have there shown that there are two sea move- 
ments of the field of view accomplished by the eyes in 
binocular vision. The first is a bodily shifting of the field of 
the right eye one-half interocular distance to the left, and 
of the field of the left eye the same distance to the right ; so 
that the two eyes are brought together in the middle and com- 
bined to form a single binocular eye, — the two visual lines 
combined to form a common visual his movement is 
habitual and involuntary, but it produces nit change in the 
apparent position | . objects unless they be very near. The 
second is a rotation of the whole field of view of both eyes 
about the afin pen whenever the two eyes move in opposite 
directions, as in convergence or divergence. This rotation is 
always in a direction opposite to the motion of the eyes, and 
us in the eee of the p enomena relat 
r 
Stationary, and the visual ieee seem to move across them 
But in binocular vision, when the two eyes move in opposite 
directions, the visual line seems to remain station (i. @., we 
seem to lo ge in ome — — while external rts or 
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= This Jour, sit. ¢ vol. i, p. 33, and vol. ii, pp. 314 and 417. 
