362 Journal of Comparative Neurology. 



the outer association layer. It is found at the ectal border of 

 the outer association layer, where this meets the II and III 

 Meynert layer. This stratum is named differently according as 

 it appears in the occipital region or elsewhere. In the occipital 

 region it is called the layer of Gennari ; in all other regions the 

 layer of Baillarger.^ At some points in the cortex, this layer 

 is doubled. In connection with these intra-cortical layers, Kaes 

 also treats the Meynert band of fibrae propriae. (See Fig. i.) 



The general course of medullation of the fiber systems of 

 the cortex is described by Kaes in detail. The account of the 

 period earlier than i y^ years, Kaes derives from Vulpius' work 

 but the description of the process subsequent to that time is 

 based upon his own investigations. The first of the fibers 

 connected with the cortex to become medullated, are the pro- 

 jection fibers. At birth they appear raying out almost as far as 

 the cortex. At about four months after birth the very first of 

 the cortical association fibers, the fibrae propriae, become medul- 

 lated.^ By eight months the first of the intra-cortical fibers be- 

 gin to appear in tlie most advanced regions.^ 



■ The description of the further development cannot be ac- 

 curately assigned to definite ages, partly because some regions 

 of the cortex d.vidop so much more rapidly than others, and 

 partly because Kae ; examined no brains between the ages of 

 I J^ and 18 years, nor between 18 and 38 years. A general 

 description of the course of development can, however, be de- 

 rived from a comparison of the different stages of advancement 

 within the same brain. The first intra-cortical fibers become 

 medullated shortly after the fibrae propriae. They appear as a 

 few scattered fibers running parallel to the layer of fibrae propriae 

 on its ectal border. Gradually these fibers increase in number, 

 spread for a short distance toward the surface of the cortex, and 

 assume a stratified appearance. This is the outer association 

 layer. ^ Before the formation of the outer association layer is 



'3.P-43; I. p- 2. 



» S, p. 41, 44. 



'5. P-4S; 6, p. 11; 8 p. 3. 



