7 o ATLAS OF NERVE CELLS 



Plate XLVII. shows three of the large pyramidal cells of the cortex (g). In this plate 

 the existence of thorn-like excrescences upon the apical process of the cell is clearly shown. 

 These are the so-called gemmules, and it will be noticed that many of them have club-shaped 

 extremities. These gemmules are similar to those already seen on the branches of the 

 Purkinje cells of the cerebellum. Their exact significance is unknown, but Berkley considers 

 them of great functional importance, and has shown J that in degenerative diseases of the brain 

 of toxic origin, they are the first part of the cell to suffer, the degenerated cell having a 

 swollen apical process without gemmules. In this plate the division of the apical process and 

 the divergence of its branches before they enter the superficial layer are well seen. 



To the right of the plate a long straight neuraxon is seen passing toward the superficial 

 layer. This may be taken as one of the terminal fibres of which so many come up from 

 the cord and basal ganglia and end in the cortex. These, of course, pass between and 

 interlace with the other systems of fibres already described, and make up a considerable part 

 of the white matter. The terminal filaments of these fibres and the terminals of their 

 collaterals enter into close relation with the cells of this layer, and they may thus bring in 

 impulses from a distance, which, being received in the pyramidal cells, set up new responses 

 in the form of motor or sensory or mental activity. 



1 The Medical News; Nov. 9, 1895. 



