THE CEREBRAL GANGLIA. 319 



which pursue quite a direct course through the external or 

 granular layer and disappear when near the periphery. The 

 primary processes, one or two in number, have a tendency to 

 spring from the cell-body at an obtuse angle, and give off at 

 almost right angles to themselves the straight peripheral pro- 

 cesses already mentioned. The nuclei of these cells are oval 

 and coarsely granular ; the nucleolus is round and small. 



The cortex proper consists of a granular matrix vertically 

 striated by the cell-processes and parallel blood-vessels. There 

 is also a moderate sprinkling of small round cells and nuclei 

 similar to those in the third layer. The cortex is very vascular. 



THE CEREBRAL GANGLIA. 



As examples of these structures the optic thalami and cor- 

 pora striata may be taken. They are collections of gray matter 

 through which part of the fibres, emanating from the crura to 

 help form the corona radiata, pass. 



In the corpus striatum these fibres pass through in bundles 

 visible to the naked eye, which gives to this body its striated 

 appearance. These bundles radiate toward the periphery of 

 the body, thus leaving ever increasing spaces between them. 

 These spaces at the base of the body, at the point of entrance 

 of the bundles from the crura, are narrow, filled with nerve- 

 fibres running in horizontal, vertical, and diagonal directions, 

 seemingly commissural in nature, and multipolar cells few in 

 number, large, and resembling somewhat cells of the anterior 

 horns of the spinal cord, whose processes mingle with the fibres 

 mentioned. Nearer the periphery of the organ, where the bun- 

 dles of fibres are more widely separated, the intervening mass of 

 fibres and cells abruptly changes to a finely granular gray ma- 

 trix, holding in its substance numerous small blood-vessels 

 and small nerve-cells, mostly round some, however, triangular 

 in shape, similar to those of the second layer of the cere- 

 bral cortex. They have large nuclei and many delicate pro- 

 cesses. 



The optic thalami consist of a mixture of gray matter and 

 fibres, not, however, so regularly arranged as in the corpus 

 striatum. The gray matter contains a few oval cells having 

 many delicate processes. 



The cerebral ventricles. Continuous with the central canal 



