658 



THE CEREBRUM 



thorny; in fact, it has been claimed that these projections form actual synaptic 

 connections with neighboring neurons. 



(c) The stellate or granular layer contains numerous cells possessing a stellate 

 shape and short irregular axons. It is also known as the middle cell lamina. 



(d) The inner fiber lamina contains numer- 

 ous large and medium-sized cells which are 

 known as the cells of Betz. The latter are not 

 present in all parts of the cerebral cortex, but 

 are most conspicuous in its motor area next to 

 the fissure of Rolando. Their axons pass into 

 the white matter. 



(e) The layer of fusiform or polymorphous 

 cells is situated next to the white matter. It 

 is also known as the inner cell lamina and is com- 

 posed of different types of cells of which the 

 spindle-shaped ones are the most prominent. 

 It also embraces a number of pyramidal cells 

 similar to those found in the outer realm of the 

 more superficial layer, but their tips are directed 

 inward and their bases toward the surface. 

 These are the cells of Martinotti. In addition, 

 this layer contains a cell resembling the second 

 type of Golgi with branching axons. The latter 

 terminate in the neighboring gray matter. 



General Arrangement of the White 

 Matter. — The medullary portion of the 

 cerebrum begins directly below the poly- 

 morphous layer. When stained in ac- 

 cordance with Weigert's method which 

 brings out the meduUated nerve fibers, 

 the white matter is seen to be arranged 

 in radial striae, i.e., its fibers expand fan- 

 Hke from a common center formed by 

 the internal capsule. Some of these ra- 

 dial streamers may be followed to the 

 surface of the cortex and may be seen to 

 give rise here and there to networks of 

 fibers which are placed transversely to 

 the course of the former. A layer of 

 this kind is found directly underneath 

 the surface of the cortex, but it does not 

 extend throughout the brain. It is 

 most conspicuous in the hippocampal 

 region. Another layer is situated be- 

 tween the molecular and pyramidal 

 zones, and still another internally to the 

 granular zone. These layers are known 

 respectively as the outer and inner 

 stripes of Baillarger. A special layer 

 of transverse fibers is found in the visual 

 area of the occipital lobe where it bisects the granular layer. This is 



Fig. 328. — Postcentral Convolu- 

 tion. Golgi Method. 

 i; Plexiform layer; 2, small 

 pyramids; 3, medium pyramids; 

 4, superficial large pyramids; 5, 

 granules; 6, deep large pyramids; 

 7, deep medium pyramids. (Cajal.) 



