574 DR JAMES W. DAWSON ON 



and engorged with blood, and in its adventitia is an increase of nucleated elements. 

 These are mostly small, round, deeply-staining nuclei with little protoplasm, together 

 with a few fat granule cells. The capillaries within the area are also dilated, but 

 changes in their walls are not marked. The presence of swollen axis cylinders in 

 cross-section and in short pieces in longitudinal can be proved in the narrow spaces 

 between the fat granule cells and the glia cell processes. 



At the periphery is a more or less broad transition zone. This shows (l) a very 

 irregular loss of myelin, the myelinated fibres showing all stages of degeneration ; 

 (2) a very marked nuclear proliferation, which in the outer part consists mostly of 

 small nuclei and in the inner part of the larger, protoplasmic cells similar to those 

 just described ; and (3) the presence of a few fat granule cells lying in the wide 

 meshes between the processes of the large glia elements. 



Marchi sections of such a small recent area (figs. 13, 68) show the central vessel 

 surrounded by concentric layers of cells filled with closely compressed fat granules. 

 Similar cells lie irregularly but closely scattered in the tissue, and the picture 

 enables one to recognise how such areas received the designation of " fat granule 

 cell myelitis." Marchi sections counter-stained with safranin and mounted in 

 Canada balsam give a very instructive picture. The fat granules within the cell 

 elements dissolve in the Canada balsam, leaving a skeleton structure of the tissue 

 with the nuclei and the processes of the large glia elements and the nuclei of the 

 fat granule cells stained with safranin. Such sections frequently gave the most 

 characteristic representation of the close relation of glia cell processes to the fat 

 granule cell — the latter apparently lying in the large meshes formed by the pro- 

 cesses of different glia cells. The Marchi preparations also showed that the fibres 

 in the transition zone were in a condition of disintegration. This degenerating 

 myelin did not dissolve out when mounted in Canada balsam — thus showing the 

 different constitution of the fat granules within the cells and the globules and 

 fragments of disintegrated myelin. 



Such an area, therefore, again consists largely of closely arranged fat granule cells, 

 between which lie the large protoplasmic proliferated glia elements ; of dilated vessels 

 with fat granule cells and other nucleated elements in their adventitial spaces ; of 

 markedly altered persisting axis cylinders ; and of a gradual transition zone in which 

 these changes are less marked and in which degenerating myelin fibres may be found. 



If now the old sclerotic areas are briefly contrasted with those which have been 

 termed recent areas, it is found that the areas typical of the " sclerose en plaques " 

 of Charcot are marked by the following histological characteristics : the complete 

 absence of myelin (Weigert stain); the presence of a dense fibrillar tissue (glia 

 stain) ; the persistence of numerous axis cylinders (silver impregnation method) ; 

 the presence of numerous blood-vessels with condensed, sclerosed walls (diffuse 

 stains) ; and the complete absence of any evidence of myelin degeneration (Marchi 



