GEOTROPISM IN ANIMALS 187 
compared with those on the dependence of movements upon 
the ear. And so it happens that Aubert and Delage! 
acknowledge the latter relation, but do not, as it seems to 
me, acknowledge the former. I myself do not doubt the 
belief of Breuer and Mach’ that the organs associated with 
the permanent changes in the position of the eyeballs, in 
movements of the head, lie in the inner ear; and I think it 
probable, in further accord with these authors, that these 
organs are more especially the otoliths. I therefore add the 
following results, obtained in a large series of experiments 
on the inner ear of the shark (Scyllium-canicula), principally 
to show that my ideas of the importance of the inner ear in 
the geotropism of the higher animals rest upon personal 
observations.’ 
I. If the otoliths are removed (either with a pair of 
forceps or a small sharp spoon) from a shark (Scyllium- 
canicula) upon one side, say the left, the following changes 
occur in the animal in its orientation toward the center of 
the earth: 
1. The animal no longer swims, as does the normal, so 
that its medium plane is vertical, but it has a tendency to 
turn the left or operated side downward at an angle of from 
20 to 50°, or even more, with the horizontal. 
2. The same change in the orientation can be noticed 
when the animal is lying quietly upon the bottom of the 
aquarium. It then frequently lies resting upon the left 
lateral fins, while the right fin often does not touch the 
bottom of the dish. 
3. When the animal is in the normal primary position, 
1AUBERT, Physiologische Studien uber die Orientirung (Ttibingen, 1888). 
2Macu, Grundlinien der Lehre von den Bewegungsempfindungen (Leipzig, 1875), 
p. 110. 
3In an addendum to his paper on the Functions of the Central Nervous System, 
etc. (Braunschweig, 1888), STEINER describes his experiments on ‘‘the semi-circular 
canals of sharks.’? This author has overlooked the fact that it is the function of the 
inner ear to call forth compensatory motions and positions, and so has failed to 
make observations on the geotropic functions of the ear. (See MAcH and BREUER.) 
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