370 



THE DEVELOPMENT OF CERTAIN FEATURES OF THE CEREBELLUM. 



unexpected from the old point of view; i. e., that the vermis is the phylogenetically 

 old and the hemispheres the phylogenetically new portion of the cerebellum. It 

 affords valuable evidence, however, in favor of the view recently expressed by 

 Edinger, that the vermis and flocculus are both phylogenetically old. Inasmuch as 

 both sides of the fissura uvulo-nodularis show like development of the Purkinje 

 cells, and as the portion of the cerebellum across this fissure from the flocculus is the 

 representative of the paraflocculus, it suggests the possibility of the paraflocculus, 

 as well as the flocculus, belonging to the paleo-cerebellum. 



In the series studied it was possible to first determine the number of Purkinje 

 cells per field in the new-born; from this time on the number remains constant, the 

 apparent decrease being proportionate to the actual increase in surface. 



TABLE B. M if run iilmlixm. 



Table B deals with microcephalies of various ages, in which the number of 

 Purkinje cells per field was determined as for table A. Upon comparing these 

 specimens with those of corresponding ages given in table A, it will be observed that 

 in the cerebellum of the microcephalic child of 22 months the number of Purkinje 

 cells is about 50 per cent of the normal, as represented by the 2-year-old child given 

 in the preceding table. In the 2-year-old microcephalic the number of cells in the 

 vermis and hemisphere is about 70 per cent of the normal, while the number in the 

 flocculus is about 90 per cent. In the adult microcephalic the number of cells per 

 field is practically normal. 



In each of these cases, however, we are dealing with a cerebellum actually 

 smaller than normal, with a total cortical area much less than normal; so that in 

 every case the actual number of Purkinje cells must be below that of the normal 

 cerebellum. In the first two specimens the reduction is due not merely to the actual 

 decrease in cortex, for even where the cortex is present there is a relative reduction 

 of 30 to 50 per cent per field. In the adult microcephalic this decrease in number is 

 directly proportional to the decrease in cerebellar cortex, inasmuch as the number of 

 cells per field is practically normal. This suggests the possibility of a delayed devel- 

 opment of Purkinje cells. In microcephalism the cerebrum, as well as the cerebellum, 

 is too small. It is possible that failure of development of the latter is secondary 

 and due to an inadequately stimulating influence from the cerebral cortex. 



GROWTH OF THE MOLECULAR LAYER OF THE CEREBELLAR CORTEX. 



Upon examination of the literature I find that Berliner (1905) is the only 

 investigator who has attempted to determine by measurements the rate of develop- 

 ment of the cerebellum at prenatal and postnatal stages. In projection drawings 



