162 H. SAXTON BURR 



RESULTS OF EXPERIMENTS 



In reporting the results of the experiments outhned above, 

 there are a few general facts which it will be well to consider 

 first. Figures 1 to 9 show three typical levels, each, from normal, 

 series I and series II cerebral hemispheres in parallel columns. 

 It is evident in general that transplantation by removing the 

 hemisphere from its normal surroundings distorts to some extent 

 the general outline of the transplant. The roughly semicircular 

 outline is changed to an oval one, with considerable lengthening 

 of the vertical axis and shortening of the transverse diameter. 

 Concomitant with this is the narrowing of the ventricular cavity. 

 The probable cause of these slight deformations is the fact that 

 the hemisphere is removed from the enveloping cartilaginous 

 covering, and placed in a portion of the body wall which is 

 relatively thin, thereby bringing considerable lateral pressure to 

 bear upon it. 



The most striking fundamental difference between the trans- 

 planted and the normal hemisphere lies in the evident reduction 

 in mass of the central gray. This diminution is e\'ident at all 

 levels of the telencephalon, although less marked, perhaps, at 

 the posterior pole. As a result, there is an apparent increase 

 in the number of peripheral fibers, although, as will be shown 

 later, this increase is only apparent, as there is a noticeable 

 decrease of fibers in certain regions. 



In considering the problem of the factors involved in stimu- 

 lating growth in the growth period, a consideration of figures 

 1 to 9 will show that little or no stimulating effect is produced 

 by the functional activity of the nasal placode. For it is evident 

 that a hemisphere without a functionally active end-organ, 

 critical levels from which are shown in figures 4 to 6, is as com- 

 pletely organized as that in which the nasal placode is capable 

 of function (figs. 7 to 9) . That this is so may perhaps be better 

 shown if one analyzes more completely the detailed organization 

 of the hemispheres. 



In order to understand clearly the effect of isolating the cerebral 

 hemisphere by transplantation, it is necessary to refer to the 



