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, 1 and Breuer has corroborated 

 this observation. 2 According to a paper by Sewall, 3 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 mo^e- 

 ments. These experimental facts, indicative of the depend- 

 ence of geotropic orientation upon the ear, are not numerous 



1 SCHRADER, PflUgers Archiv, Vol. XLI. 



2 BREUER, Pfliigers Archiv, Vol. XL VIII, p. 237. 



3 SEWALL, Journal of Physiology, Vol. IV. 



