CHANGES IN HUMAN CEREBELLUM WITH AGE 29 



('94), who correlated the anatomical changes in the cerebellum 

 of man and several lower animals with the development of motor 

 control. 



The most detailed statement I have found on the growth of 

 the myelin sheaths in man is from Berliner ('05) , and I am quot- 

 ing it in full: 



I have studied more carefully the myelination of the nerve plexus 

 in the granular layer of the vermis. Already in the child of one to 

 two months single^ myelinated fibers, mostly from the Purkinje cells, 

 can be seen distributed radially; in the fourth month these are more 

 numerous and can be followed to the top of the folium. No myelinated 

 tangential fibers can yet be seen. These appear first at five months; 

 they run below the Purkinje cells and can be seen easier at the bottoms 

 of sulci than at the tips of the folia. In the seventh month the my- 

 elinated plexus of the granular layer is well developed; in the ninth 

 month the plexus and the association fibers are still further myelinated; 

 and in the child of fifteen months the association fibers have become 

 still clearer. 



From Berliner's statement it will be seen that myelination is 

 taking place while the layer of external granule cells is disappear- 

 ing and while the child is developing motor control. The growth 

 of myelinated fibers continues for some time, however, at a 

 rather rapid rate after the external granule layer has completely 

 disappeared. 



Judging from the results of Engel ('63), there is often a loss 

 or shrinkage of myelinated fibers in the cerebellum during senes- 

 cence, and this naturally has to be inferred in view of the dis- 

 appearance of the cell bodies of the Purkinje cells as shown in 

 this paper. To what extent the axones of other cells may dis- 

 appear or atrophy during senescence I do not know. 



THE DENTATE NUCLEUS IN SENESCENCE 



INIost of the axones from the Purkinje cells in the lateral lobes 

 of the cerebellum terminate in the dentate nucleus, and I have 

 examined therefore the cells of this nucleus to determine \vhat 

 changes take place there during old age. For this purpose T 

 have not attempted to use exact methods, but have sunply 

 examined the sections carefully under high and low powers of 

 the microscope. 



