NERVOUS TISSUES AND SYSTEMS. 87 



The white matter consists of meduttated fibres and neuroglia. 

 There are two kinds of neuroglia cells in the cerebellum: First, 

 small rounded cells, which occur in the granule layer and send a 

 few processes downward and many longer processes outward to the 

 molecular layer; second, stellate cells, which are found in all the 

 layers. 



CEREBKTJM. 



The cerebrum comprises the cerebral cortex, medulla, and ventri- 

 cles. 



The cerebral cortex is composed of five layers which merge im- 

 perceptibly into each other. They are : 



( 1 ) Molecular Layer. This is superficial, and is finely granular, 

 with an interlacing of medullated fibres and a reticulum of neu- 

 roglia. The cells of Caji are found in this layer. 



(2) Layer of Small Pyramidal Cells. This is composed of gan- 

 glion cells which are pyramidal in form. They send out several 

 apical and lateral dendrites, which penetrate the molecular layer 

 and, by continuous division, produce a complicated network. The 

 axis cylinder proceeds from the basal end of the cell and, after send- 

 ing out a few collaterals, enters the medulla. 



(3) Layer of Large Pyramidal Cells. This differs from the pre- 

 ceding in the size of its cells. The axis cylinder process enters the 

 medulla to become a medullated fibre. 



(4) Layer of Irregular Cells. This is composed of cells, oval or 

 polygonal, which are devoid of apical dendrites. Each axis cylinder 

 sends out collaterals and then enters the medulla to become one or 

 two nerve fibres. 



(5) The Layer of Fusiform Cells. This lies adjacent to the 

 medulla and is composed of a few spindle-shaped cells with ner^e 

 fibres between them. The cells are arranged parallel with the course 

 of the fibres. 



The medulla. This comprises the white matter of the cerebrum, 

 and is composed of medullated fibres and connective tissue struc- 

 tures. 



The ventricles. The gray matter of the ventricles, like that of 

 the cerebral cortex, is composed of multipolar ganglion cells, neu- 



