440 Gforgc L. Strfrtrr, M.D. 



appendage are typical, and there is establishment of normal 

 appearing nerve and ganglion connections. 



EQUILIBRATION 



It was found in the experiments performed a year ago that 

 removal of one or both ear vesicles, just after they are pinched oft 

 from the skin, produces in the tadpoles definite disturbances in 

 the development of their power of equilibration. It was found 

 that when a tadpole is deprived of but one ear vesicle he is by 

 virtue of the remaining one able to develop practically normal 

 swimming abilities; but when both ear vesicles are removed the 

 results are more serious, and in that case the tadpole never de- 

 velops any sense of equilibrium and is never able to swim. The 

 loss is not compensated for by any other organ and the animal 

 lies helpless on the bottom of the dish. With one ear vesicle the 

 tadpole swims practically in normal fashion, and with noearvesi- 

 cle he cannot swim at all. 



The fact that one ear vesicle is sufficient for the maintenance ot 

 equilibrmm greatly smiplifies the study of this mechanism; it 

 means that one side can be immediately eliminated, and the prob- 

 lem is reduced from a bilateral one to a unilateral one. A series of 

 experiments at once suggested themselves, in which the ear vesi- 

 cle of one side was to be removed, and then various operative 

 procedures undertaken upon the ear vesicle of the opposite side, 

 and the test oi its consequent functional ability was to be the very 

 decisive one of whether the animal could swim properly, or 

 whether it could not swim at all. 



In the paper referred to there is described the experiment of 

 transplanting the ear vesicle into a subdermal pocket in front of 

 the eye. When this was done the transplanted ear vesiclecontinued 

 in its development, and in some instances established a nerve-gan- 

 glion connection with the forebrain; but such specimens never gave 

 evidence of functional activity. The failure to functionate was 

 not unexpected, inasmuch as the connections established were 

 at an abnormal situation, and furthermore the vesicles though 

 having developed many essential features of the normal labyrinth 



