2 ROBERT S. ELLIS 



the cerebella of eighteen idiots and imbeciles whose brains are 

 in The Wistar Institute Museum. On the disappearance of the 

 layer of external granule cells I have reviewed the work of Vignal 

 ('89), Berliner ('05), Biach ('09), Lowy ('10), Takasu ('05) and 

 Addison ('11), and I have verified their conclusions by a study of 

 a number of cases of human cerebella. For the relative thick- 

 nesses of the molecular, internal granular, and fiber layers, I 

 have reviewed the work of Engel ('63), Krohn ('92), and Roncor- 

 oni ('05) and I have added some original measurements. Mate- 

 rial for satisfactory measurements of the growth in size of the 

 Purkinje cells has not been available, but I have made a few 

 measurements on such cases as I could obtain. I have counted 

 the Purkinje cells in two areas of both hemispheres of sixty-three 

 cerebella from negroes, whites, and mulattoes of both sexes and 

 of ages ranging from twelve to ninety-two j^ears, and have com- 

 pared these results with those already reported. On the growth 

 and degeneration of the myelin sheath I have reviewed the work 

 of Engel ('63), Lui ('94), de Sanctis ('98), Berliner ('05) and Lowy 

 ('10). 



Finally I have studied the degeneration of the cells of the den- 

 tate nucleus in senescence. 



Many of the papers discussed are, it is true, rather old, but I 

 have felt justified in bringing these various data together in order 

 to get a general view of the different changes in the cerebellum 

 during life and of the relation of these to variations to functional 

 efficiency. 



THE WEIGHT OF THE CEREBELLUM 



Perfectly satisfactory weights for the human cerebellum during 

 the early stages of growth are not available, and hospital material 

 probably gives results which are below the average for the popu- 

 lation at large. It is consequently not surprising that the weights 

 recorded by different observers show more or less variation. 



Boyd, in England, made extensive records of the weights of 

 the parts of the brain, as well as of other organs, and these have 

 been compiled and published by Sharpey ('61), and by IMarshall 



