736 



THE NERVOUS SYSTEM. 



Microscopical Appearance of the Cortex. The cortex presents a remarkable 

 structure, consisting of two distinct layers viz. an external gray or cellular layer, 

 and an internal rust-colored granular layer. Between the two layers, or rather 

 situated in the deepest part of the gray or cellular layer, is an incomplete stratum 

 of the characteristic cells of the cerebellum, the corpuscles of Purkinje. 



The external gray or cellular layer (Fig. 436) consists of fibres and cells. The 

 fibres are delicate fibrillse, some running at right angles to the surface-fibres of 

 Bergman. These are the dendritic processes of large glia-cells situated in the gran- 



External gray or 

 cellular layer. 



Corpuscles of Purkinje. 



Internal or rust- 

 colored layer. 



- White substance. 



Fio. 436. Vertical section through the gray matter of the human cerebellum. Magnified about 100 diame- 

 ters. (Klein and Noble Smith.) 



ular layer. On reaching the periphery these fibres expand into small cones, bases 

 superficially, and here form a delicate supporting connective-tissue-like membrane, 

 which spreads out into a broad base against the inner surface of the pia mater. 

 Other fibres are horizontal, and can be observed to unite, by means of a T- or Y- 

 shaped junction, with the long axis-cylinder processes of the granule-cells in the 

 granular layer. 



The cells are small, and are in two layers, outer and inner. . All have numer- 

 ously branching axis-cylinder and protoplasmic processes, the former of which, 

 from the inner cells (basket-cells), give oft' descending vertical branches which 

 ramify like a basket around the corpuscles of Purkinje. 



The corpuscles of Purkinje (Fig. 436) are flask-shaped cells in the deepest part 

 of the external gray or cellular layer, resting against the internal rust-colored 



