570 



THE NERVOUS SYSTEM 



laterals both in the immediate neighborhood of the cell and somewhat deeper 

 along its course. 



In the superficial layer of the cortex there is a peculiar type of small cell, 

 first described by Cajal. Most of these cells are fusiform in shape, with the 

 long axis parallel to the surface of the convolution. They give off usually two 

 axones which run along parallel to the surface and send down numerous 



r 



FIG. 401. 



FIG. 400. Typical Pyramidal Cell from the Human Cortex, a, Cell body; b, main dendrites 

 with gemmules; c, lateral dendrites; d, axone and collaterals. Only a small part of the axone 

 is shown. (Bailey.) 



FIG. 401. Showing the Stages in the Development of a Pyramidal Cell. (Ramdn y Cajal.) 



fine collaterals at right angles. Another form of Cajal cell, triangular or 

 quadrangular in shape, is also seen. Both forms have, as a rule, more than 

 one axone. Their collaterals pass in a horizontal direction, forming a 

 fine band of fibers, known as tangential fibers. A third type of cell is the 

 fusiform or polymorphous. Some of these are strictly fusiform in shape and 

 lie with their axes parallel to the surface of the convolution. They give off 

 protoplasmic processes which pass down toward the white matter, some of 

 them turning to run in a horizontal direction. The fusiform and polymorphous 

 cells are grouped in the same layer. 



