THE CORTICAL GRAY MATTER. IQ5 



may be seen dividing the cortex into two gray layers. This line 

 was first seen and described in the visual area by Gennari and, 

 ten years later, by Vicq d'Azyr. 2. The external layer of large 

 pyramids is replaced by a layer of stellate cells 25/z in diameter. 

 These stellate cells give off three or four strong processes which 

 appear to arborize in the line of Baillarger. They are found in 

 the receptive and psychic visual areas but not elsewhere in the 

 cerebral cortex. 3. The internal layer of large pyramids is* re- 

 placed by a conglomerate made up of three varieties of pyramids. 

 From without inward there are: First, small inverted pyramids, 

 cells of Martinotti, which extend their axones out toward the 

 surface. Second, the scattered giant pyramids, 25-30/1 in dia- 

 meter, arranged in a single row and called the solitary cells of 

 Meynert. The axones of the giant pyramids probably pass into 

 the optic radiation. Third, a layer of medium-sized pyramids. 



Olfactory Cortex. All the divisions of the rhinencephalon 

 are here mentioned, though only a part of them need be described :. 

 the olfactory bulb, triangle, parolfactory area, anterior perforated 

 substance, gyrus subcallosus, septum pellucidum, gyms supra- 

 callosus (longitudinal striae), fasciola cinerea, fascia dentata, 

 hippocampus, subiculum and uncus. The posterior inferior 

 part of the hippocampal gyrus and the gyrus cinguli are ordinarily 

 included in the rhinencephalon; but, according to Elliot Smith, 

 they belong to the neopallium (Figs. 26, 28 and 62). 



The cortex of the olfactory bulb (Fig. 63) is divided into five 

 layers as pictured by Barker. These five layers are as follows, 

 named from the surface toward the center: (i) The stratum 

 nervosum, composed of the T-branched fibers from the olfactory 

 nerve and their collaterals. These fibers run nearly parallel 

 with the surface for some distance, then bend centrally and break 

 up into their end-tufts in the second layer. (2) The stratum 

 glomerulosum is made up of round bodies, called glomeruli, which 

 are composed of the end-tufts of olfactory nerve fibers and of 

 brush-like dendrites from the spindle and mitral cells of the third 

 and fourth layers. The glomeruli constitute the synapses between 

 the first and second olfactory neurones. (3) The stratum retic- 

 ulare. This is a network of mitral dendrites interwoven with 



