268 Journal of Comparative Neurology. 



which leave straight or spiral-shaped canals for the non-staina- 

 ble substance which carries the fibrils. It would be a grave 

 error to see in the structure anything characteristic for anything 

 ' motor. ' We have no real knowledge of the difference of the 

 neural activity in afferent and efferent elements. If we call 

 the one * motor ' it is only justified on account of its connec- 

 tion with a muscle. There are indeed cells of stichochromous 

 type in the medulla oblongata — the large cells of the reticular 

 substance, and also the cells of Deiter's nucleus, which are cer- 

 tainly not motor in the sense that they would go to muscles, 

 but it is not improbable that they terminate around real motor 

 neurones and have the character of inter-segmental neurones 

 for the motor elements. There are similar cells in the spinal 

 segments, and it would be decidedly unwise to think that from 

 the structure of the cell-body alone we would be able to read 

 its functions. This stage of neurological knowledge is not yet 

 reached. 



3. T/ie cerebral afferent neurones. The cerebral mechan- 

 isms have been studied with more persistence than any other 

 part of the nervous system since the so-called cerebral localiza- 

 tion did away with the diffuse and misty views of Flourens. 

 Nevertheless our actual knowledge is yet far from being a 

 knowledge of neurones and of their accurate connections. 



Even those who work more especially on the cerebral cor- 

 tex, will have to admit that the knowledge of the cortex stands 

 in its very infancy. Conjectures are certainly numerous ; there 

 is also no lack of description of layers and, lately, even of cell- 

 types ; also medullated fibers have received their share of atten- 

 tion ; but neurones ? cell-bodies with all their processes and 

 terminations ? We are just approaching an almost perfect 

 knowledge of a few types of elements and the best known sim- 

 ple elements (Cajal's cells) are least knowable as to their func- 

 tions. This may be the reason why von Monakow, one of the 

 best investigators of the nervous system contents himself with 

 a description of the 'gray matter' and the 'white matter,' just 

 as of olden times when a fiber did not call for a cell with ab- 



