630 



THE NERVOUS SYSTEM 



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 



PIG. 393- 



FIG. 394. 



393- Typical Pyramidal Cell from the Human Cortex, a, Cell body; 6, main 

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

 part of the axone is shown. (Bailey.) 



FIG. 394. Showing the Stages in the Development of a Pyramidal Cell. (Ram6n y 



Cajal.) 



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

 morphous cells are grouped in the same layer. 



Besides these cells \\e find scattered through the cortex a considerable 

 number of the neuroglia cells. The character and position of these are 

 shown in figure 395. 



The general arrangement of the layers of the cortex is described very dif- 

 ferently by the various authors. It is not uniform in the different parts of the 

 brain. The simplest and most representative type, however, of the arrange- 



