PHOTOMECHANICAL CHANGES IN THE RETINA OF 



NORMAL AND TRANSPLANTED EYES OF 



AMBLYSTOMA LARVAE 



HENRY LAURENS AND J. W. WILLIAMS 



Oshorn Zoological Laboratory, Yale University 



THREE TEXT FIGURES AND ONE PLATE 



INTRODUCTION 



The changes in form and position of the visual cells and their 

 nuclei and of the pigment in the retinal epithelium is a subject 

 concerning which a vast literature has been accumulated. 

 There are, however, points here and there concerning which our 

 knowledge is incomplete. One of these is the influence of the 

 central nervous system upon the photomechanical changes. The 

 work which has been done has been recently reviewed by Det- 

 wiler ('16) and by Arey ('16 b). From this experimental evi- 

 dence it appears that photomechanical changes may take place 

 after the optic nerve has been cut, i.e., independently of central 

 control. 



Amblystoma larvae, normal, eyeless, and individuals with 

 transplanted eyes, were being used extensively in experiments 

 on the physiology of the melanophores and it was decided to 

 make a study of the reactions of the retinal pigment and of the 

 visual cells of these animals to light and darkness. It occurred 

 to us that the investigation of the effects of light and darkness 

 on transplanted eyes would be a method devoid of certain ob- 

 jections that might be raised against the sectioning of the optic 

 nerve which involves shock and degeneration. Such a trans- 

 planted eye is not only under no normal nervous control but has 

 never been so. There is a chance that nerve fibers, both spinal 

 and autonomic, may grow into the eyeball, but the chance is 

 indeed slight, and still less that they could exert any influence 

 on the movements of the retinal elements. 



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