1178 



HUMAN ANATOMY. 



with the collaterals and similarly directed processes from other cells, take part 

 in producing the felt-work giving rise to the outer stripe of Baillarger. From 

 the deeper or basal surface of the cell arises the delicate centrally directed axone, 

 which, penetrating the intervening fourth layer, acquires a medullary coat and 

 enters the white core of the convolution as one of the component nerve-fibres. 

 The axone gives of? one or more collaterals which, after a shorter or longer 

 course, establish relations with other and often remote cells. In addition to the 

 two chief processes, the peripherally directed apical dendrite and the centrally 

 coursing axones, a variable number — from four to twelve — of secondary lateral 



dendrites spring from the basal 



Fig. ioi6. 



Small pyra- 

 midal cells 



Large pyra- 

 midal cells 



'olyniorphic 

 cells 



t^-A 



Nerve-cells of 

 pregnation. X 90. 

 fessor T. G. Lee. 



cerebral 

 Drawn 



cortex as seen after silver im- 

 from preparation made by Pro- 



angles of the cell. These processes 

 usually divide dichotomously, each 

 succeeding pair of branches in turn 

 splitting into twigs, until the den- 

 drite is resolved into an end-brush 

 of fibrillae which aid in producing 

 an intricate felt-work of finest 

 threads. Each pyramidal cell con- 

 tains a conspicuous spherical or 

 ellipsoidal nucleus, within which a 

 distinct nucleolus is usually distin- 

 guishable. The cytoplasm exhibits 

 a striation and, in addition to the 

 masses of tigroid substance, the 

 Nissl bodies, a mass of brownish 

 pigment granules. The larger 

 pyramidal cells are surrounded 

 by an evident pericellular lymph- 

 space. 



The layer of polymorphic 

 cells includes a large number of 

 small nerve-cells, from .008 — .010 

 mm. in diameter, whose forms 

 vary greatly, irregular, spherical, 

 triangular, stellate and fusiform 

 elements being present. Small 

 pyramidal cells are also often seen 

 within this layer. In contrast to 

 dendrites of the typical pyramidal 

 cells, those of the polymorphic 

 elements, although peripherally 

 directed, do not reach the stratum 

 zonale but end before gaining the 

 outermost layer. Their axones 

 pass into the subjacent fibre- 

 layer. The radial disposition 

 of the groups of fibres within 

 the deepest stratum of the 

 cortical substance limits the 

 polymorphic cells chiefly to the 

 consequently appear arranged in a 



interfascicula. areas, within which the cells 

 somewhat columnar order. 



Within the deeper layers of the cortex, therefore among the polymorphic 

 and the pyramidal elements, two additional varieties of nerve-cells are encountered. 

 These are the cells of Martinotti and the cells of Golgi. 



The cells of Martinotti are of small size and triangular or spindle-form in 

 outline and particularly distinguished by the unusual direction of their axones. 

 These processes pass towards the surface and within the stratum zonale divide 

 into branches, which are continued horizontally in the felt-work of tangential fibres. As 



