186 STUDIES IN GENERAL PHYSIOLOGY 
There is a second, better observed and more accurately 
studied, effect of gravitation upon higher animals. This has 
to do with the axes of the eyes, which are also compelled to 
assume a definite position with reference to the horizontal. 
If the head of a fish is forcibly brought into a different posi- 
tion from that which it occupies normally with reference to 
the center of the earth, the eyes tend to reassume, either 
entirely or in part, their old orientation. These lasting 
changes in the position of the eyeballs with reference to the 
axes of the head which accompany a permanent change in 
the position of the head are also present, as is well known, in 
human beings. They can in this case, as in the case of 
animals, be compensated through appositely working optical 
conditions or internal stimuli, but a definite force exists in 
this case also to compel the axes of the eyes to assume 
their proper angle with the horizontal. 
Light has nothing to do with these phenomena; they 
occur also, as is well known, in the dark, and in persons 
totally blind. 
We deal rather in these cases, as we know, with the 
activities of a definite organ, namely, the inner ear. Schrader 
found that frogs from which the inner ear has been removed 
upon both sides no longer endeavor to regain their position 
when laid upon their backs,’ and Breuer has corroborated 
this observation.* According to a paper by Sewall,? to 
which I do not, however, have access, and with which I am 
acquainted only from the abstract which Breuer gives of it, 
the compensatory movements of the eyes in sharks and skates 
were seriously affected by such lesions of the labyrinth as 
led to decided and permanent disturbances in their move- 
ments. These experimental facts, indicative of the depend- 
ence of geotropic orientation upon the ear, are not numerous 
1ScHRADER, Pfliigers Archiv, Vol. XLI. 
2BrREvER, Pfliigers Archiv, Vol. XLVIII, p. 237. 
3SEWALL, Journal of Physiology, Vol. IV. 
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