THE NERVOUS SYSTEM. 



621 



stance. This arrangement is shown in the accompanying figures (373 

 and 373A). The gray matter of the brain contains, however, not only 

 these layers and cells, but an infinitely rich mass of fibres, which can be 

 shown by various stains to have a certain definite arrangement. Some 

 of the fibres are vertical in direction, passing directly up to the most 

 superficial layers of cells; others have a horizontal direction, dividing 



Fig. 373. The principal constituent elements of the gray cortical layer of the anterior 

 cerebrum. (After Ramon y Cajal.) 



the gray matter into different layers. These layers of fibres have re- 

 ceived different names. They vary somewhat in accordance with the 

 area of the cortex examined. A typical arrangement is shown in fig. 

 374. The most conspicuous are certain large triangular or pyramidal 



