138 LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



plexus, as well as near the point of origin of the lateral ones 

 there are some minute perforations (Key and Ret/ius). The 

 middle one of these foramina in the medullary tube is called 

 the foramen of Magendic. It is of great importance in obvi- 

 ating sudden changes of pressure in the cerebro-spinal fluid. 



Into the above-described mass of the cerebellum pass the 

 three pedunculi on each side. They pass into the large central 

 mass of white substance, and from there become united with 

 gray nuclei and send fasciculi to the cerebellar cortex. 



Little is known as to the connections and course of these 

 cerebellar fibres. We know that they pass from the central 

 white substance through a granular layer containing nerve and 

 glia cells, that they extend beyond this and enter some peculiar, 

 large, branched cells, the ganglion-cells -of Purkinjc ; that the 

 processes of these latter bodies repeatedly divide and pass to 

 regions just under the surface of the cerebellum. Apparently 

 these processes enter into some sort of relation with a net-work 

 of horizontal and oblique fibres situated in this part of the 

 cortex. These bend around and pass back through the granular 

 layer to the white substance after anastomosing and interweav- 

 ing freely with each other. A general idea of their course may 

 be obtained from the dark lines in the accompanying figure. 

 Many more fibres return from the cortex than pass to its large 

 cells, a fact which can be explained by the ramifications of its 

 cell-processes. All parts of the cortex are connected with each 

 other by peculiar garlanded bundles of fibres, which closely 

 follow the cortical elevations and depressions. 



The cerebellum also presents collections of gray matter 

 aside from that in the cortex. On each side, in the midst of the 

 white substance of the hemispheres, there lies a large convoluted 

 nucleus, the corpus ciliare or corpus dentatum. Internal to it 

 other collections of gray matter are met with ; first, the embolus, 

 then the nucleus globosus, a longish nucleus with a tuberosity 

 at its posterior extremity ; and lastly, lying farthest inward, is the 

 nucleus tegmenti (nucleus fastigii). 



