rfx;exeratiox tx the braix of amrlystoma 



I. THE REGENERATION OF THE FOREBRAIN 



H. SAXTOX BURR 



The Audtinnicdl Lnhoratori/ of The School of Medicine, Yale Cniversity 



KOIH FIOl'RES 



Up to the present time the data deahng with regeneration in 

 the central nervous system have been exceedingly conflicting. 

 The early workers reported the regeneration of \ari()iis definitive 

 parts after they were extir])ated. As far hack as 1890 Danielew- 

 sky found that the removal of the cerebral hemispheres of the 

 frog residtcd in the formation of a 'cerebral mass' which he 

 believed contained embiyonic nerve cells, though this mass 

 was in no way a new licinisphci-c. More recently Bell, in 1007, 

 removed the "lateral half" of the brain of the frog and found 

 that the brain nearly always is rcfornuMl though never does it 

 reach the normal size. 



On the other hand. Schaper ('98) found tiiat the icinoval of 

 ])ortions or of the entire brain of Rana esculenta was never 

 followed by regeneration. Rubin in 190;^ working with Rana 

 fusca larvae found that no regeneration occurred aftei- the re- 

 moval of the brain or of ])arts (^f it. 



The results of experiments published elsewhere (Burr '10) 

 show conclusively that the nasal placode of Ambly stoma and 

 also of the frog does not regenerate when it is com})letely re- 

 moved. In addition, the large amount of work by Lewis and 

 others has shown that the eye ^^^ll not regenerate when all of 

 the anlage is remo\ed. It was deemed probable, therefore, 

 that complete extirpation of the cerebral hemisphere would not 

 be followed by even a partial regeneration of the part removed. 

 The discrejiancy in the results previously reported might be 

 due to incomplete operations. The regeneration of parts of 



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