348 THE BODY AT WORK 



but since they are not, like the granules of the cerebellum, 

 coloured by the chrome-silver method, their form and the dispo- 

 sition of their axons are unknown. (4) Large pyramids exactly 

 similar in form to the small ones. Their apical processes are 

 very thorny. Their axons give off several collaterals. Pyra- 

 mids are the most conspicuous elements in the cortex. 

 Properly speaking, they do not occur in layers, but are scattered 

 throughout its whole thickness, although their cell-bodies are 

 not seen in either its most superficial or its deepest strata. The 

 largest are those of which the axons either descend into the 

 spinal cord or pass to a very distant region of the cortex. 

 They are found singly or in small clusters in the deeper 

 levels. (5) Polymorphous cells, some of them pyramids lying 

 on their sides, or even directing their axons towards the surface ; 

 some fusiform or irregular cells ; some Golgi-cells (p. 340). 

 The axons of pyramids enter the white matter, and many 

 fibres from the white matter radiate towards the surface be- 

 tween the pyramids ; but the way in which afferent, sensory 

 fibres are connected with the collecting processes, dendrites, 

 of the pyramids is not known. We have already referred to 

 thorns, and to the possible nerve-net (p. 301). Sheets of 

 tangential fibres also occur in the cortex. A particularly 

 distinct sheet divides the granules in the visual cortex into two 

 strata. In sections of this region the sheet of fibres appears as 

 a white line, distinctly visible without a lens. 



The limits of the several areas can be determined by ex- 

 amining the structure of the cortex ; but the individual pecu- 

 liarities of the various regions are not so marked as to indicate 

 that they have different kinds of work to do ; if by kinds of 

 work we wish to imply that one part is " sensory," another 

 " motor," a third concerned with " intellectual processes." 

 On the contrary, its relative uniformity shows unmistakably 

 that all parts are engaged in the same work. Nevertheless, 

 certain broad conclusions can be drawn with regard to the form 

 of the neurones more immediately concerned with sensation, 

 with motion that is to say, with the discharge to the grey 

 matter of the cerebro-spinal axis of the impulses which call its 

 neurones into activity and with the secondary processes, 

 called collectively " association," which occur within the cortex. 

 Granules, as everywhere throughout the nervous system, are 



