f 
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into clear consciousness phenomena which 
underlie so much of our daily conduct. 
3. The last point which I wish to touch is 
again the much discussed question of upright 
vision. I feel like apologizing for bringing up 
this question again; but I am convinced that 
much of the difference of view is the result of 
misunderstanding. For example, I explain 
upright vision by the law of direction. Now, 
surely, Professor Cattell must misunderstand 
the explanation when he talks of standing on 
one’s head and still seeing things upright as 
controverting that law. The law of direction 
explains uprightness equally well, whatever be 
the position of the observer. I am sure the 
question has been obscured and the mystery in- 
tensified by that wonderful inverted retinal 
image. But seeing things upright is not 
necessarily connected with an inverted image. 
It is easy to imagine an eye so constructed 
that the retinal image shall be upright, and 
yet by the law of direction the object shall 
also be seen upright. We probably have some- 
thing like this realized in the case of insects. 
The compound eye of insects is so constructed 
of slender tubes lined with pigment that only 
the central rays of each radiant pencil can 
reach and impress the retina, all others being 
quenched by striking on the sides. This, as 
shown by the figure, would make an upright 
Fia. 1. Diagram showing the upright image in the 
eye of an insect. 
image, and yet by the law of direction the ob- 
ject would be seen upright also. Our retina is 
concave instead of convex. It is so because the 
image is inverted, and, therefore, must be re- 
inverted in the act of outward reference. 
The marvellousness of the inverted image has 
diverted attention from the real question, which 
is, the seeing things in their true places. A 
child only afew days old will turn the eyes 
* SCIENCE. 
[N. 8. Vou. VI. No. 150. 
toward a bright light. Is en anything so 
mysterious in this? But why toward, unless it 
saw the light in its true direction? Now, up- 
right vision is only a case under this more gen- 
eral fact; for objects are made up of an infinite 
number of lights or radiants and each is seen 
in its true direction, and, therefore, the object 
in its true position. 
Professor Cattell refers to the recent experi- 
ments of Dr. Stratton* as controverting the law 
of direction, although he thinks a much easier 
way of doing so ‘is to stand on one’s head.’ 
I am glad to have the opportunity to express 
my admiration of these experiments of Dr. 
Stratton, and my high estimate of their value ; 
and I cannot think that the simpler mode sug- 
gested by Professor Cattell would be at all an 
adequate substitute. In brief, the experiment 
consists in the wearing of inverting glasses con- 
tinually for eight days. The experimenter for 
that length of time never saw things except re- 
versed. The ground was above and the sky 
below, things on the right were seen on the left, 
and vice versa. And yet by the end of the ex- 
periment all the movements of the body were 
so adjusted to the new conditions that he could 
walk the streets with comparative comfort. 
This seems very extraordinary, and it is pos- 
sible that we may have to reconstruct some of 
our fundamental conceptions of space; but evi- 
dently it does not controvert the law of direc- 
tion. If we only think a moment, we shall see 
that we already have phenomena approaching 
in various degrees the extreme conditions of 
this experiment, but they are so familiar that 
they do not strike us with wonder. In looking 
ina mirror one image is partly inverted, 7. e., 
it is turned about a vertical axis—it is inverted 
from side to side, but not up and down. And 
yet, we easily adjust our movements to the 
changed conditions. We make complex movye- 
ments, such as tying a cravat, with ease and 
accuracy. 
Again, in looking through a microscope the 
image of the object is completely inverted, 7%. e., 
it is turned about the visual axis 180°; and, 
yet, with a little practice, we adjust our move- 
ments to the new conditions. We slide the 
object in all directions accurately and even 
* Psych. Rey. for July and September. 
