442 George L. Streeter, M.D. 



Throughout the whole period of observation they had exhibited 

 incoordinate movements, and at the end of that time they were 

 unable to swim. This and the two previous operations indicated 

 that rotation of an ear vesicle, or transplanting it from one side 

 to the other, or fragmenting it was not compatible with the devel- 

 opment of its function, in spite of the fact that the ear vesicle pro- 

 ceeded in its development and had become to all appearances 

 almost a perfect labyrinth. In the next experiments less severe 

 treatment was tried. 



d Left ear vesicle removed; right ear vesicle uncovered and 

 carefully lifted out and then immediately placed back in its orig- 

 inal position, the effort being made to do a minimum amount of 

 injury. Of six specimens all exhibited symptoms of the absence 

 of all sense of equilibrium. 



In the experiments a, b, c and d there was the possibility of 

 injury to both the nerve-ganglion connection and the ear vesicle. 

 In the following experiments the effort was made to restrict the 

 injury to one or the other. 



e Left ear vesicle removed; right ear vesicle uncovered and 

 a fragment cut from the cephalic portion of its wall, care being used 

 not to otherwise disturb the vesicle. Eight such specimens were 

 kept five weeks, and none of them developed any sense of equilib- 

 rium, or were able to swim. 



/ Left ear vesicle removed; right ear vesicle uncovered and 

 a small piece cut from its caudal border, any further disturbance 

 being avoided as in e. Eight specimens were operated upon, and 

 after keeping them four weeks none of them could swim properly. 



g Left ear vesicle removed; longitudmal incision made through 

 skin on right side just dorsal to ear vesicle, and needle passed 

 down between the neural tube and ear vesicle and moved back- 

 ward and forward so as to sever its nervous connection without 

 otherwise disturbing the ear vesicle or loosening it from the skin. 

 None of the four specimens studied swimmed properly, though 

 one of them could swim somewhat, but was easily confused bv 

 any excitement and then made wild and ill directed movements. 

 It was thought that the ear vesicles in these cases would escape 

 injury; but examination of the specimens when cut in serial sections 



