TRANSPLANTATION OF HEMISPHERES 161 



and connected with the telencephalon, functional activity of the 

 olfactory epithelium was possible, while discharge of peripheral 

 stimuli from secondar}^ to tertiarj^ centers was prevented by the 

 removal of the telencephalon from the rest of the brain stem. 

 In series III the same conditions obtained as in series II, though 

 reached by a different method. 



In the course of the above experiments it developed that in 

 addition to data on the problem just outlined, interesting pictures 

 would appear of the fiber-tract organization of the cerebral 

 hemisphere which had been removed from the possibility of tracts 

 entering it from the lower centers of the brain stem. Also it 

 became evident that some light would be thrown on the formation 

 of the choroid plexus and on the nourishment of the transplanted 

 structures in strange surroundings. 



The experiments of series III were subsequently discarded, 

 since it was found that the presence of a foreign body in the 

 brain substance resulted in the rapid proliferation of the cells 

 in the immediate vicinity of the block, forming many multiple 

 cavities with a marked deformation of the walls of the neural 

 tube. This made it impossible to analyze with any surety the 

 effect of- the operation on the hemisphere so isolated. The for- 

 mation of 'Polymyelie' has been noted frequently in the literature, 

 notably by Waelsch ('14), who produced multiple cavities experi- 

 mentally in the spinal cord of chick embryos by means of knife 

 thrusts piercing the wall of the central canal. This tendency of 

 nervous tissue to proliferate aberrantly was noted frequently in 

 the course of these experiments, hence great care was necessary 

 not to injure the wall of the cerebral hemisphere in transplanta- 

 tion. That sections of the central nervous system can be trans- 

 planted without the formation of such pathological manifesta- 

 tions was shown by Hooker ('15). The expermients of series I 

 and II have shown that the operation is entirely feasible, though 

 very slight injury will produce all manner of distortions. 



