544 THE NERVOUS SYSTEM. 
The stratum zonale is chiefly composed of fibres which run in a tangential direction, or, 
in other words, parallel to the surface. These form an interlacement of consilerable density 
and extreme complexity. The elements which for the most part enter into the formation 
of this feltwork are: (1) the terminal filaments of the apical dendrites of the pyramidal 
cells; (2) the terminal 
wevroaia . filaments of certain corti- 
rancentiaL = Cipetal fibres, which enter 
Pies the cortex from the white 
centre of the gyrus ; (3) the 
Sa vrerew  2XOnS Of celtain small cells 
peculiar to this stratum ; (4) 
the axons pf the cells of 
Martinotti., Spread over 
the surface of this tan- 
gential inerlacement of 
fibres, whicl constitutes the 
most imporant part of the 
stratum zoule, there is a 
thin layer ofieuroglia which 
intervenes etween it and 
pad Rerrrs the pia matr, which covers 
or the convaution. The 
BAILLARGER = stratum zonle isnot devoid 
of nerve-clls, although 
these are siall and some- 
what indefiite in their con- 
nexions. ‘he most char- 
acteristic frm is a small 
fusiform cd described by 
Cajal, whic sends out from 
either enda long process 
and which ks in the deeper 
part of te layer. The 
long filamatous processes 
of this cell tireac their way 
Pelwrracortica. Detween theothe fibres in 
fl ASSOCIATION a tangential diretion and 
give off mhute branches 
which pass) tovards the 
surface. | 
The deepet laver of the 
cortex contins she poly- 
morphic cells ‘hese cells 
Fic. 405.—D1acram To ILLUstRaTE MINUTE STRUCTURE OF THE . are not larje, nd they 
CEREBRAL CORTEX. present mary ifferent 
= Neuroglia cells. a ae ee et fons ih haar 
C,. Cell with short axon (N) which breaks +. Cell of Martinotti. Pate au pay fe se 
up in a free arborisation. H. Polymorphic cell. this group, bu|nor of these 
D. Spindle-shaped cell in stratum zonate. K. Corticipetal fibres. reach the stutua zonale, 
and in this resect the 
polymorphic cells offer a marked contrast to the pyramidal cells, The axos of the 
polymorphic cells, however, like those of the pyramidal cells, enter the wlite entre of 
the gyrus in the shape of nerve-fibres. | 
In addition to the cells characteristic of the several layers, there are tvo wich may 
be found amongst the pyramidal or amongst the polymorphic cells. These are: (1 the cells 
of Golgi; (2) the cells of Martinotti. 
A cell of Golgi has this peculiarity—that its axon, close to its origin, begins 5 divide, 
and very soon loses its individuality by breaking up into a perfect maze of ranches, 
none of which pass far from the neighbourhood of the cell-body and none of wh:h enter 
the stratum zonale. 
The cell of Martinotti is small and is chiefly found in the deeper part of th cortex. 
Its leading peculiarity is, that its slender axon runs in a contrary direction to thexons of 
the pyramidal cells and of the polymorphic cells. In other words, it proceeds toards the 
‘at 
STRATUM 
ZONALE 
LAYER OF 
SMALL PYRAMIDALCELLS 
CELLS 
SUPRA RADIAL FELTWORK 
LAYER OF 
PYRAMIDAL 
LARGE 
RADIAL FELTWORK 
INNER BAND 
= | BAILLARGER 
OF 
INTER 
LAYER 
