444 George L. Streeter, M.D. 



have a normal nerve ganglion connection with the brain at the 

 proper place, and yet the specimen may not have given signs of 

 any functional activity on the part of that organ. 



Spemann'' is doubtless mistaken in attributing the disturbance 

 in equilibrium simply to the alteration in the planes of the canals. 

 He reports some experiments in which at an early stage a skin flap 

 was turned back, and the ear vesicle taken out and replaced in 

 various positions; and in such specimens he observed faulty equi- 

 librium, and on sectioning his material the vesicle seemed to lie in 

 an abnormal position, and this he assumes to be the cause of the 

 abnormal movements observed. On the one hand, wax plate 

 reconstructions of misplaced ear vesicles show that in my cases they 

 regain their proper position, and the canals eventually lie in their 

 normal planes; the specimens nevertheless continue to make inco- 

 ordinate movements. On the other hand, in those experiments 

 where the normal position of the vesicle, as regards the planes 

 of space, was undisturbed the results were equally serious. My 

 own experiments suggest that the difficulty lies not so much with 

 the end organ as with the central connections, and perhaps further 

 experiments in that direction would furnish additional infor- 

 mation upon this subject. 



CONCLUSIONS 



The primitive ear vesicle ot the tadpole may be loosened from 

 its normal position and rotated in various directions, so that its 

 axes lie in abnormal planes, and notwithstanding such interfer- 

 ence it eventually develops into a labyrinth which is right side up 

 and exhibits the normal relations to the brain and the surrounding 

 structures. When transplanted to the opposite side of the body, 

 if placed in the acoustic region, it likewise assumes a normal 

 posture. Judging from these facts, the posture of the labyrinth 

 is controlled by its environment. 



The "laterality" of the labyrinth is determined before the clo- 

 sure of the ear vesicle. When the left ear vesicle is transplanted 



' Spemann, H., '06: Ueber embryonale Transplantation. Verhandl. der Gesell. Deutscher Naturf. 

 u. Aerzte. 78 Vers. Stuttgart. 



