22 ROBERT S. ELLIS 



THE PURKINJE CELLS 



Growth in size 



In the human cerebellum the full number of Purkinje cells is 

 present at birth; they are, however, undeveloped and rather 

 immature in form. The successive stages through which they 

 pass in the growth process have been described in some detail by 

 Cajal and others, but for my purpose it is sufficient to note that 

 by the end of the first year the cells have assumed their adult 

 form. 



I have not had satisfactory material for determining the in- 

 crease in the diameters of the Purkinje cells, but I have made 

 measurements on twelve cases ranging in age from eighteen days 

 to three years. Because of variations in the treatment to which 

 the different brains were subjected, I do not consider the abso- 

 lute measurements of sufficient value to present them in tabular 

 form. Two results may, however, be stated with a fair degree 

 of assurance. First, the cells are larger in the vermis than in 

 the hemispheres during the first few months of life. Second, 

 the growth in size during the first six months is very rapid, but 

 becomes slower in rate thereafter, and the cells appear to have 

 practically their full size by about twelve to eighteen months. 

 The growth curve has essentially the same form as that shown for 

 the molecular layer in chart 5. 



This difference found in the vermis adds to and confirms the 

 other differences already pointed out. There can, I think, be 

 no reasonable doubt that typically the vermis develops in ad- 

 vance of the hemispheres. 



The decrease in the number of cells with advancing age 



In addition to work already reported, I have made cell counts 

 on the cerebella of sixty-three negroes, whites, and mulattoes 

 of both sexes and of ages ranging from twelve to"ninety-two years. 

 All of the material is from The Wistar Institute Museum. 



The technique and the method of making cell counts have 

 been the same as that reported in my earlier paper (Ellis, '19). 

 To put the matter briefly, I have made corrections for differences 

 in the size of different cerebella and for the efi'ect of shrinkage of 



