THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 623 



arch with its convexity either on the surface or within the radiating fibres, and 

 the outline of these areas which seemed to pass definitely over into the sub- 

 cortical white matter was, as a rule, much sharper than that of those confined 

 to the cortex (<?/. Pis. LXIII-LXIV). 



The close disposition of the numerous areas in certain convolutions gave place 

 often to a coalescence, with a complete demyelination of cortical tissue extending 

 over the whole of one convolution and sometimes round the cups of the adjoining- 

 convolutions. This demyelination in some cases affected the cortex irregularly, and 

 the resultant line might further be broken into by wedge-shaped or bow-shaped 

 areas extending further inwards (fig. 276). Short of complete coalescence of the 

 areas, there were found stretches of the cortex which presented a moth-eaten 

 appearance, in which only islets of the normal radiations or intra- or supraradial 

 network of fibres were retained. Such a moth-eaten appearance was specially well 

 brought out when the section was cut in a plane at right angles to the radiations 

 (fig. 295). It is perhaps necessary to emphasise that such descriptions are taken 

 .from specimens in which it could be stated almost definitely that the demyelination 

 was not due to over-differentiation. The limits of such areas are quite defined ; the 

 adjoining convolutions have their tangential fibres and the fine fibres of the supra- 

 radial network well brought out ; and the demyelination often corresponded exactly 

 to the area of supply of the superficial vessel plexus of the cortex (cf. figs. 271-272), 

 although no single larger vessel could be brought into relation to it. Such an 

 extensive affection of the cortex, too, is often limited to certain convolutions. 

 Siemerling and Raecke, Sanders, Schob, and others have pointed out similar 

 extensive involvement of the cortex, and Alzheimer and Spielmeyer in general 

 paralysis have noted the existence of demyelinated areas involving the cortex 

 extensively, in which none of the cellular changes of general paralysis were 

 present. 



The remarkable symmetry of the cortical areas is again sufficiently indicated in 

 figs. 271-273, in one of which symmetrical areas on either side of an individual 

 sulcus may be noted (fig. 273). 



In the cerebellum the cortex often shares in the extensive involvement of the 

 cerebral cortex. Here the medullary cores of individual folia may be simply cut 

 across, or the fine reticulum of nerve fibres in the granular layer may be also 

 affected : at other times, especially in the flocculus, the trunk of numerous medullary 

 cores is cut across, and this involvement spreads to affect individual branches and the 

 corresponding reticulum of fibres, while immediately adjoining cores, with the 

 pertaining cortical reticulum, are unaffected. A striking parallelism may be presented 

 in the two flocculi (figs. 27-28) — the peduncles of which may also be involved in an 

 extension from the angles of the IVth ventricle. 



It is thus seen that the areas are apparently distributed over the whole central 

 nervous system, that their form can be related only in a modified way to two basal 



