268 INTRODUCTION TO NEUROLOGY 



of Baillarger is greatly thickened by the optic projection fibers, 

 and here it is sometimes called the line of Gennari. The por- 

 tion of cortex exhibiting the line of Gennari is called the area 

 striata. 



The most characteristic neurons of the cortex are pyramidal in 

 shape, with the apex directed toward the outer surface of the 

 brain and prolonged to form the principal dendrite. Smaller 

 dendrites arise from other parts of the cell body, and the axon 

 arising from the base of the cell body is directed inward into the 

 white matter (Figs. 7, 8, pp. 42, 44). The cortex contains, more- 

 over, many other types of neurons, some of irregular shape (poly- 

 morphic or multiform cells) and many whose axons are short and 



Fig. 122. Sections of the cerebral cortex, drawn nearly natural size and 

 showing the naked-eye appearance: 1 shows the layers as they appear in 

 many parts of the cortex, and 2 shows the appearance of a section from the 

 visual cortex (area striata) from the neighborhood of the calcarine fissure, 

 with the conspicuous line of Gennari. (After Baillarger.) 



ramify close to the cell body without leaving the cortex itself 

 (Fig. 9, p. 44). These type II neurons probably assist in the 

 summation and irradiation of stimuli (see p. 101). Some other 

 types of neurons are shown in Fig. 123. 



Figure 124 illustrates a typical arrangement of the neurons in 

 the postcentral gyrus (gyrus centralis posterior of Fig. 54, p. 121). 

 Most of the neurons here shown send their axons inward to 

 participate in the formation of the white matter and may dis- 

 charge their nervous impulses into remote parts of the brain. 

 The endings of the afferent nerve-fibers which effect synaptic 

 connection with the neurons here shown form a dense entangle- 

 ment of fine unmyelinated fibers between the dendrites of these 

 neurons. These afferent fibers are not included in Fig. 124; one 



