Some experiments on the developing ear vesicle of the tadpole with relation to equilibration / by George L. Streeter.

  • George Linius Streeter
Date:
1906
Catalogue details

Licence: In copyright

Credit: Some experiments on the developing ear vesicle of the tadpole with relation to 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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    mechanical stimuli by flexion of the body and tail.1 These reac- tions consist of simple motor reflexes at first, but they soon become combined and coordinated so that by a series of such body flexions they are able to wiggle rapidly forward on the bottom of the dish. This manner of progression evidently consists entirely of spinal cord reflexes and is not controlled by higher centers. In order to perform it, it is necessary for the tadpoles to touch the bottom or Fig. 2 Fig. i. Outline drawing of normal tadpole (Rana sylvatica) of the second stage or stage of spinal reflexes. Enlarged 8 diameters. Fig. 2, Outline drawing of normal tadpole (Rana sylvatica) at the beginning of the third stage. This specimen had the power of equilibration, although sections of the ear vesicle showed that the development of the semicircular canals was not yet complete. Enlarged 8 diameters. side of the dish; when they are driven up into the free water with a pipette, where there is no contact with solid objects, they make no effort at movement, but sink inertly to the bottom; on striking the bottom they run forward again. The third stage begins when they are first able to move freely about without touching solid 11 have been informed by Dr. R. G. Harrison that it is just at this time that the motor nerve roots make their appearance, and this may determine the onset of the second stage. According to fcis observations the power of muscle contraction follows almost immediately after the development of the motor roots; but it never precedes their development, as is maintained by some. He has found the motor root present in specimens that had not yet moved.
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