18 ROBERT S. ELLIS 



I have examined twelve cases with ages ranging from eighteen 

 days to eleven months and my results agree so closely with the 

 curve given by Biach that I have not thought it necessary to 

 modify his statement. 



Lowy ('10) has studied the external granule layer in a number 

 of birds and mammals. He likewise finds that the vermis is in 

 advance of the hemispheres in the disappearance of the external 

 granule cells. To this he adds the observation that there seems 

 to be a tendency for the cells to disappear faster in the anterior 

 (cephalic) part of the hemispheres than in the posterior. I 

 have studied this in my cases of human cerebella, and although 

 the difference is not a great one, amounting to about one row of 

 cells usually, I consider it to be fairly distinct in the majority of 

 the cases examined. This, theoretically, is what we should ex- 

 pect according to the localization theory of Bolk ('05-'07). 



Takasu ('05) has studied the pig and finds there a difference 

 between the vermis and the hemispheres similar to that already 

 noted. 



Addison ('11), working on the albino rat, does not find any con- 

 spicuous difference between the vermis and the hemispheres, but 

 he does find that the area anterior to the primary sulcus is some- 

 what in advance of the area posterior to it. Also he finds the 

 paraflocculus to be most retarded of all. As the paraflocculus 

 has been regarded as the center for coordination of tail move- 

 mentSj this appears to me to be a significant observation. 



Biach, in connection with his normal cases, also studied the 

 cerebella of twenty-three infants who had died from diseases 

 tending to produce arrest of general development or other ab- 

 normalities in the nervous system. Out of the twenty-three 

 cases, ten showed a distinct retardation in the rate of disap- 

 pearance of the external granule cells; some showed no great 

 variation from the normal, while others were too old to make it 

 certain that they had not been retarded. It is significant, how- 

 ever, that nearly half of his pathological cases do show a corre- 

 lation between inferior function and retarded disappearance of 

 the external granules. Later I shall consider more specifically 

 the functional significance of the disappearance of this layer of 

 cells. 



