EFFECTS OF DISLOCATION OF EYE UPON GOLDFISH. 65 



On the 2yth of June the dislocated eye was removed from the 

 artificial orbit and slid again along the channel into the original 

 orbit. This operation is also a very easy procedure and can be 

 done without obvious injury of the eye or of the animal. 



The animal, as most Anamnia, recovered very slowly from 

 anesthesia and therefore we began our observations on the 

 following day (June 28). The fish was in the normal position at 

 rest and during locomotion. In the several weeks following, the 

 orientation and locomotion were constantly normal, no tilted 

 positions were observed. The other goldfish showed also two 

 weeks after the operation the above described tilting and the 

 tilting reached its maximum six weeks after the dislocation. The 

 results obtained in our second experiment corroborate completely 

 the observations on our first fish with dislocated eye, since in the 

 second animal tilting and the return of vision occurred also 

 synchronously. 



At no time during the experiment did the animal show any 

 abnormalities other than the tilting. There were never any 

 evidences of circus movements, etc., which may follow injuries of 

 the midbrain, medulla and labyrinth (Steiner, 4 Loeb, 5 Bethe, 6 

 Bigelow, 7 ). 



DISCUSSION. 



"A normal fish has a delicate sense of the distance involved in 

 swimming in a straight line. This is shown by the remarkable 

 skill with which he avoids obstacles; in swimming around his 

 aquarium constantly, he strikes his nose directly against the side 

 of the tank comparatively rarely. This is not so with a fish 

 deprived of all his otoliths or with all his macular nerves severed. 

 Such fish seems to have little idea of the extent of a forward swim. 

 He is often restless and frequently alters the direction of his 

 progression" (Lee, 3 ). In his experiments Lee did not include 

 the positive side of the role of vision in the orientation and equi- 

 librium of the fish. Lee says, "When left to himself, the blinded 

 fish swims normally in all respects, moving gracefully, easily, and 

 without timidity, and shooting and diving like an uninjured fish." 



The first question which confronts us is, of course, the cause and 

 mechanism of the tilting following the eye dislocation. There 

 can be little doubt that the tilting is directly due to the dislocation 



