600 DR JAMES W. DAWSON ON 



corresponded to a zone of denser sclerosis — the vessels, however, in which had dilated 

 adventitial sheaths rilled with very numerous cellular elements. Only one distinct 

 ependymal granulation (fig. 455) could be found throughout the whole investigation : 

 this consisted of a dense mass of deeply-staining glia nuclei and glia fibrils. The 

 ependymal epithelium over it and over the whole sclerotic tissue in general, was 

 retained and apparently normal — any apparent proliferation of epithelial cells could 

 be traced to the oblique level of the section. 



The histological structure of the peri-ventricular areas need not be entered into 

 in any detail. Weigert sections showed the complete absence of myelin in the areas 

 at all stages — the preserved nerve fibres passing into the areas were very tortuous 

 and varicose. Marchi preparations (figs. 181, 308) again gave the long rows of fat 

 granule cells in the tissue spaces and around all the blood-vessels, especially around 

 the groups of venous vessels at both posterior and anterior horn : the branches of 

 these vessels could be traced for long distances towards both occipital and frontal 

 poles, and similarly numerous vessels could be traced into the lateral peri-ventricular 

 tissue. The closely arranged longitudinal fibres of the corpus callosum (fig. 307) 

 showed beautifully the tubular arrangement of the fat granule cells, the rows of 

 enlarged spider cells, and the gradually increasing dense longitudinal fibril formation. 

 Both Cajal's and Bielschowsky's methods and diffuse stains showed the very large 

 number of retained axis cylinders. When the immediately sub-ependymal tissue had 

 reached the stage of dense sclerosis, it presented an extremely close fibrillar web, 

 poor in nuclei — the fibres mostly parallel to each other, parallel to the direction of 

 the normal nerve fibres. Numerous dilated vessels twined in this fibrillar tissue. 

 Before the onset of this advanced sclerosis the glia meshes were often very elongated 

 and rarefied (fig. 376) ; the glia cells were markedly drawn out in a longitudinal 

 direction, and showed often a nucleus at each pole, and a sheaf of fine fibrils passing 

 from each pole of the cell to interlace with similar bundles of fibrils. 



In the zone of unaffected tissue around the ventricle it was found that there was 

 frequently a proliferation of the sub-ependymal glia cells. But such areas sometimes 

 showed a lighter staining of the myelin : similar " shadow " areas often united wholly 

 demyelinated areas of the lateral wall or extended inwards from them. It could 

 thus be assumed that the originally primary areas became fused by these transition 

 areas becoming wholly demyelinated, till the whole ventricular surface was affected. 



Around the aqueduct of Sylvius and around the floor of the fourth ventricle and 

 its lateral angles (cf. figs. 76-82) the degree of sclerosis was often very marked. 

 The extent of this in individual cases is well brought out in the very numerous 

 figures taken from Weigert sections, and is more fully described elsewhere in the 

 individual cases. Its structure was everywhere on similar lines. The final web 

 formed was simply an exaggeration of the closely arranged fibrils, which are 

 normally oriented in all directions. The involvement of the cranial nuclei in this 

 extension has been also elsewhere described, 



