FUNCTION AND FUNCTIONAL STIMULUS. 145 



as far as functional stimulus is concerned. These differences 

 must therefore be caused by other non-specific factors. In 

 order to ascertain how far-reaching is the influence of light, it 

 was necessary to determine the average rapidity of regeneration 

 in every group of eyes of the same series and make a curve for 

 each series. Although these curves are not yet completed, the 

 results thus far obtained show no differences between light 

 and dark series at all. Even the quantity of the regeneration is 

 therefore uninfluenced by light. 



From the above data we must draw the following conclusions: 

 Functional adaptation plays no part either in transplantation 

 or in regeneration of the retina; nor is it a factor which determines 

 either the quality or the quantity of these processes. 



This, of course, does not mean that regeneration or trans- 

 plantation of the eye cannot be influenced at all by chemical 

 or physical factors. On the contrary, as is shown by the dif- 

 ferences between transplanted eyes of the same series, examined 

 at equal intervals of time after transplantation, the quantity 

 of regenerative processes, viz., the rapidity of regeneration are 

 subject to variation by one or more factors. The point of im- 

 portance is the fact that these factors are not connected with 

 the specific functional stimulus, viz., light. Apparently they 

 are the same factors which also affect the rapidity of the re- 

 generative process of other organs. The factor concerned is 

 probably the length of time since circulation in the transplanted 

 eye was reestablished. 



Hitherto the regeneration of the retina has been considered 

 as being different from the regeneration of the bones. It was 

 supposed that a bone could only regenerate its architectural 

 structure if in use, otherwise the result would not be a normal 

 bone but a disorderly bony mass. 



Aug. Bier, 1 however, has shown that even the bones do not 

 regenerate as a mere indefinite mass of bone if kept without 

 functional stimulus, but that on the contrary, in the absence 

 of any such stimulus, they resume their original functional struc- 

 ture to the minutest details. In certain experiments a con- 

 siderable part of a human tibia was removed. Although these 



1 Aug. Bier, " Beobachtungen iiber Knochenregeneration," Arch. f. klin. Cliir., 

 Dec. 1912, c, 91. 



