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of the cerebellum 1). Now, the cortex-layer, as well in the middle 

 region of the cerebellum as at the bottom of the grooves is only one 

 cell thick. Towards the top of the region lying between these two 

 grooves the cortex-layer gradually increases in thickness, reaching in 

 the upper part of this region a thickness of three to four cells. The 

 same relation is found in the region lying behind the second groove; 

 here the epithelial stratum attains a thickness of four to five cells. 

 Towards the taenia the epithelial stratum grows thinner and thinner, 

 being at last only one cell thick upon the posterior border of the cere- 

 bellum and upon the taenia (Fig. 6). 



This observation on the structure of the epithelial layer seems to 

 me of interest, because it proves the views of Bolk on the mode of 

 development of the cerebellar cortex to be correct. Bolk concluded 

 from his gross-anatomical observations that in the cortex of the cere- 



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Fig. 6. 



Fig. 5. Structure of the rafe cerebelli. 180/1. Camera lucida drawing. /• Inter- 

 mediate layer. M. matrix layer. R. rafe. V.q. fourth ventricle. 



Fig. 6. Structure of the taenia cerebelli. 180/1. Camera lucida drawing. C. cortex- 

 layer, c.p. capillary. /. intermediate layer. 31. matrix-layer. T. taenia. 



bellum there ought to be centres of increased growth and that the 

 folding of the cortex should take place perpendicularly on the direction 

 of this increased development. 



In my opinion the thickened parts of the cortex-layer represent 

 the centres of increased growth of Bolk. 



The taenia deserves special description. As said above, the cortex- 

 layer is continued upon the taenia as an epithelial stratum one cell 

 thick (Fig. 6 C). Upon the taenia the epithelial cells as well as the 

 nuclei belonging to these cells grow smaller. The matrix-layer {M) 



1) I am unable to give the exact diagnosis of the grooves, because 

 I do not have sufficient material for comparison. 



