Meyer, Data of Modem Neufology. 271 



ation of the external geniculate body according to whether the 

 eye or the occipital cortex is removed, and that this finding is 

 interpreted by Forel in favor of his neurone-concept. If the 

 eyes are removed, the end-arborizations of the optic nerve fibers 

 in the * ground-substance ' of the external geniculate body will 

 decay ; consequently the cells will come more closely together, 

 part of the ground-substance being resorbed ; if however the 

 cortex is destroyed the optic radiation is affected and its cells 

 will undergo atrophy and even resorption and neuroglia forms 

 the scar. (See Monakow's Gehirnpathologie, Fig. 82 and '^'^. 

 We must remember that the resorption is most complete where 

 the lesion occurs in very early life. The general law is easily 

 demonstrated in the spinal cord of cases of infantile hemiple- 

 gia where the degenerated direct pyramidal tract is often resorbed 

 without leaving a neuroglia scar, and the area of the degener- 

 ated crossed pyramid is very much smaller than in the case of 

 hemiplegia in the adult or senile. 



(2). Among the cerebral efferent neurones we really are 

 familiar with the pyramidal systems only. The thalamic radia- 

 tion and even the efferent paths to the cranial nerves are not 

 accurately enough known to allow us to speak of complete neu- 

 rones, although the latter have been much cleared up by 

 Hoche. All bodies of the efferent ' motor' neurones belong to 

 the pyramidal type, a cell-form which undoubtedly owes its out- 

 line to the peculiar composition of the cortex in layers with 

 more or less perpendicular radiation of fibers. Among the 

 many forms of cortical cells the large motor pyramidal cells 

 are quite characteristic, not only by location but by structure. 

 These are the ones which von Gudden and von Monakow 

 have shown to be absent after destruction of the internal cap- 

 sule in the young. 



These large cells of the motor region are located in the 

 deeper parts of the fourth layer of Cajal ; the most striking 

 ones are the giant pyramids of the paracentral region, between 

 the layer of small cells and the polymorphous. They are among 

 the largest cell-bodies of the human nervous system, perhaps 

 because a correspondingly long neurite comes from them. The 



