278 



THE NERVOUS SYSTEM 



that has been rolled into the ventricle along the line of the hippocampal fissure. 

 Upon its ventricular surface it is covered by a thin layer of white matter, known 

 as the alveus, through which the fibers arising in the hippocampus reach the 

 fimbria and the fornix. Beginning at the line of separation from the fascia 

 dentata, we may enumerate the constituent layers of the hippocampus as fol- 

 lows: the molecular layer, the layer of pyramidal cells, and the layer of poly- 

 morphic cells (Figs. 209, 210). 



The molecular layer contains a superficial stratum of tangential fibers derived 

 from the corresponding layer of the subiculum and from bundles of fibers that 



Fig. 209. Cross-section of the hippocampus and hippocampal gyrus of man. (Edinger.) 



perforate the cortex of the subiculum (Fig. 210). More deeply placed is another 

 fiber layer, containing collaterals from the pyramidal cells as well as collateral and 

 terminal fibers from the alveus, and known as the stratum lacunosum. The 

 molecular stratum in the hippocampus resembles that in other parts of the cortex 

 in containing the terminal branches of the apical dendrites from the pyramidal 

 cells, and a few nerve-cells which for the most part belong to Golgi's Type II. 

 The Layer of Pyramidal Cells. The pyramidal cells are all of medium size 

 and their fusiform bodies are rather closely packed together, forming a well- 



