A STUDY OF THE DEVELOPMENT OF CERTAIN FEATUEES OF 



THE CEREBELLUM, 



BY BURTON D. MYEKS. 



Through the kindness of Professor von Monakow, it has been my privilege to 

 study fifteen sets of serial sections of brains of different developmental stages,* 

 selected from very extensive collections in the Institute of Brain Anatomy at Zurich. 

 This study has special reference to certain features of cerebellum. The following 

 report is confined to a brief description of observations on the growth of the Pur- 

 kin je cells, the growth of the molecular layer of the cerebellar cortex, and the ratio 

 of medullary to cortical zones in cerebellum. For the sake of conciseness, each 

 subject will be considered separately throughout all stages of development. 



PURKINJE CELLS. 



In the many investigations on the cerebellum that have been published during 

 the past twenty years, in only a few instances has attention been directed to the 

 Purkinje cells. An examination of the literature covering this limited field reveals 

 the fact that investigators have interested themselves for the most part with the 

 relations, internal structure, and histogenesis of these cells. Popoff (1895) came 

 to the conclusion that they arise exclusively from the deepest cells of the outer 

 nuclear layer. Omer (1899), in a study of the Purkinje cells in the sheep and guinea 

 pig, found that they are derived from non-granular cells of ill-defined contour in 

 the outer nuclear layer. Cajal (1907) directed attention to displaced Purkinje 

 cells, annular terminations around the cell-bodies, and neurofibrils in the proto- 

 plasmic aborizations of the cells. No attention has been given by these authors 

 to the determination of the portion of the cerebellum in which the Purkinje cells 

 first make their appearance, or to the possible bearing this may have upon the 

 problem of what, in the cerebellum, is phylogenetically old and what is phylogenet- 

 ically new. Furthermore, no determination has ever been made as to the number 

 of Purkinje cells that are to be found at the different stages of development, nor 

 have the questions which this point might help to solve received consideration. It 

 was to this untouched field, therefore, that the present investigation was directed. 



The Purkinje cells are first definitely demonstrable at the sixth month of intra- 

 uterine life. The cortex of the cerebellar hemisphere of a fetus of this age is shown 

 in figure 1, a drawing with a projection apparatus in which the greatest care has 

 been taken to show every cell of the field in position. A few Purkinje cells are seen 

 along the rather sharp line of demarcation between the nuclear and molecular layers. 



*The scries was as follows: 



1. Fetus from middle part of 4th month. 



2. Fetus from early part of 5th month. 



3. Fetus from latter part of 5th month. 



4. Fetus from Gth month. 



5. Fetus from 7th month. 



6. New-born child. 



7. Child, 16 days. 



8. Child, 3 weeks. 



9. Child, 3 months. 

 1U. Child, 2 years. 



11. Adult. 



12. Miorocephalic child, 22 months. 



13. Microcephalic child, 2 years. 



14. Mieroeephalic adult, 46 years. 



15. Hemiatrophic cerebellum. 



367 



