8 



LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



In a scries of communications (1872-1881) and later, in a 

 lamer work on " The Course of Nerve-tracts in the Brain and 



O 



Spinal Cord" (1876), he has shown that the various tracts of 

 fibres which look so much alike on all sections of the adult 

 brain are markedly differentiated during the embryonic period, 



CcH 



Bdf 



ilaf 



Fcp 



Cca 



The fibres of the corpus callosum, shown by tearing the hardened specimen with forceps. 



(Aftei- Henley 



by the fact that they acquire their medullary sheaths at different 

 times. Whole "systems" in the cross-section of the spinal cord 

 are still clear and transparent at a time when others are white 

 and contain medullary substance. The following up of these 

 white portions, in both cross and longitudinal sections, is very 

 much easier, and gives very much more certain results than 



