1024 HISTOLOGY OF CEREBELLUM. [BOOK in. 



belong to small nerve cells of a peculiar nature. In these cells 

 the nucleus is surrounded by cell substance which, forming a thin 

 layer immediately around the nucleus, is chiefly disposed as thin 

 spreading branches, some of which end in a peculiar arborescence 

 not unlike a muscle end-plate ; these processes contribute with 

 the neuroglia to form the reticular looking bed spoken of above. No 

 process can be traced inwards to the central white matter ; but one 

 of the processes gives off a branch, which passing vertically outwards 

 takes on the appearance of a delicate axis cylinder process and 

 runs, without dividing, into the molecular layer for a variable 

 distance, sometimes reaching close to the surface, but at last 

 divides at right angles into two fibrils, which run in the longitudi- 

 nal plane in opposite directions for a considerable distance, and 

 are ultimately lost to view. Since these cells in the nuclear layer 

 are very numerous and each gives rise in the above manner to 

 longitudinal fibrils, the molecular layer is traversed by a multitude 

 of fibrils, visible as such in longitudinal sections but appearing as 

 dots in transverse sections, in which the cells of Purkinje are best 

 displayed. 



Besides these longitudinal fibrils proceeding from the cells of 

 the nuclear layer, special modes of preparation similarly disclose 

 numerous transverse as well as more or less oblique fibrils. Many of 

 these appear to result from the branching of the small nerve cells 

 of the molecular layer, and some of those so arising descend to the 

 layer of the cells of Purkinje and end around the bodies of those 

 cells in remarkable nests of fibrils, without however actually 

 making connections with them. 



The medullated fibres of the central white matter of a lamella 

 pass on all sides into the nuclear layer ; or, put in another way, 

 medullated fibres passing out of the nuclear layer at all points 

 converge to form the central white matter. Some of these fibres 

 as we have seen begin, or end, in the cells of Purkinje. None of 

 them appear to join the cells of the nuclear layer, and we have no 

 evidence that any of them end or begin in any way in the nuclear 

 layer. A certain number, however, may be seen to pass through 

 the nuclear layer and between the cells of Purkinje into the 

 molecular layer, where losing their medulla they divide and 

 apparently contribute to the numerous fibrils of the molecular 

 layer. The presumption therefore is that all the fibres of the 

 white matter begin or end either in the cells of Purkinje or the 

 fibrils of the molecular layer. 



The superficial grey matter of the cerebellum then resembles 

 the grey matter of the spinal cord in so far as it consists of branch- 

 ing nerve cells, nerve fibres, and nerve fibrils embedded in neu- 

 roglia ; but the disposition and features of the several factors are 

 peculiar. We may take perhaps as the key of the structure the 

 fibrils of the molecular layer ; this layer is relatively very thick, 

 about 400 /z, much thicker than the nuclear layer which, however, 



