Chap, xviii.] CEREBRUM ANL CEREBELLUM. 159 



white matter. The other processes, sooner or later in 

 their course, branch and break up finally into the 

 nerve ground network of the grey matter. (4) A thin 

 stratum of small irregular branched ganglion cells, the 

 granular formation of Meynert. (5) A last stratum 

 of spindle-shaped and branched ganglion cells, ex- 

 tending parallel to the surface. 



207. According to Meynert, the grey cortex of the 

 posterior portion of the occipital lobe about the sulcus 

 hippocampi consists of eight layers, the granular for- 

 mation being the principal one. In the grey cortex of 

 the cornu Ammonis, on the other hand, the third 

 layer is the principal layer, the fourth being wanting. 

 In the claustrum (part of the wall of the Sylvian 

 fissure), the spindle-shaped cells of the fourth layer 

 form the principal stratum. 



208. The Imltms olfactoriiis contains in most 

 mammals, but not in man, a small central cavity 

 lined with columnar ciliated epithelial cells. The sub- 

 stance of the bulb around this cavity consists of an 

 upper part, which is white matter, and is a continua- 

 tion of the tractus olfactorius. The lower part is 

 grey matter, and contains the following layers, count- 

 ing from below upwards : (1) a layer of non-medul- 

 lated nerve-fibres, each with a neurilenima ; this layer 

 forms farther on the olfactory nerve going to the 

 olfactory organ ; (2) the stratum glomerulosum, com- 

 posed of a number of glomeruli or convolutions, 

 each of which consists of an olfactory nerve-fibre, and 

 in addition to it numerous small neuroglia cells ; (3) 

 stratum gelatinosum of Lockhart Clarke, composed 

 of a fine nerve network, and embedded in it multi- 

 polar ganglion cells ; (4) a last and thickest layer of 

 nuclei embedded in a network of fibrils, and similar in 

 structure with the " nuclear layer." 



209. IY. The mcsencepltalon. The fourth 

 ventricle above the upp-sr part of the pons Varolii 



