Some factors in the development of the amphibian ear vesicle and further experiments on equilibration / by George L. Streeter.

  • Streeter, George Linius, 1873-1948.
Date:
1907
Catalogue details

Licence: In copyright

Credit: Some factors in the development of the amphibian ear vesicle and further experiments on equilibration / by George L. Streeter. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    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 He 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 of 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., ’o6: Ueber embryonale Transplantation. Verhandl. der Gesell. Deutsdier Naturf. u. Aerzte. 78 Vers. Stuttgart.