THE HISTOLOGY OF DISSEMINATED SCLEEOSIS. 557 



representing the structure of the patches in the cerebral cortex, and gives a less 

 confusing picture than the iron-hsematoxylin stain. 



For the representation of the ganglion cells, Unna's polychrome methylene blue 

 was used as the modification of Nissl's method. At first introduced by Nissl as an 

 elective stain to reveal a certain portion of the ganglion ceils (the chromatophile 

 granules), this method was found to stain not only these granules but certain 

 component parts of the cell nuclei, not only ganglion cells and glia cells, but 

 connective-tissue cells, and all cell elements in the vessel walls. It stains specially 

 beautifully young actively proliferating elements, e.g. the nuclei, protoplasm, and 

 protoplasmic processes of glia cells in proliferation. Nissl's method was the first 

 which made possible the study of the finer internal structure of the cellular 

 constituents of the central nervous system, but it threw no light upon the ele- 

 mentary fibrils in ganglion cell bodies, nor upon the relation of the glia fibrils 

 to the glia cell bodies. For the latter the glia methods above mentioned 

 have been adopted, but for the former none of the neuro-fibril methods have been 

 used in this study. 



Van Gieson's method was used as the routine diffuse stain. Such sections 

 revealed the changes in the blood-vessel walls and the relation of the structural 

 elements of the tissue to one another. In densely sclerosed areas, however, the 

 distinction between axis cylinders and glia fibrils was not sufficiently brought out. 

 The Kulschitsky-Pal sections were also counter-stained with picro-fuchsin to bring out 

 the relation of the vessels to the sclerosed areas. 



Heidenhain's iron-hsematoxylin is a diffuse stain which, as already mentioned, 

 stains the medullated sheath of the nerve fibre, the axis cylinders, and the glia 

 fibrils, but in addition it stains the cell elements of the tissue. This renders the 

 interpretation of the picture a little difficult, but allows of the recognition of the 

 relationship which exists between the different structural elements. This is of great 

 importance in the study of cortical areas of sclerosis, as it brings out the changes in 

 the nerve cells, the glia cells, and the medullated fibres. The medullated sheath of 

 the nerve fibre and the axis cylinder are stained in different shades of greyish blue, 

 the nuclei of the cellular constituents of the tissue have their chromatin structure 

 well brought out, the protoplasm of the nerve cells is pale yellow, and the chroma- 

 tophile granules a deep blue. As the medullated fibres are decolorised before the 

 complete structure of the nuclear elements is brought out, it is necessary to have 

 preparations in differing degrees of differentiation. 



Numerous other stains were used to bring out individual points, e.g. Weigert's 

 elastic tissue stain, Mallory's connective-tissue stain, Gram's stain, Ford-Robertson's 

 palladium methyl-violet stain, and Scharlach R., etc. Many sections stained by 

 Levaditi's silver method for the spirochaeta pallida were also examined, but with 

 negative results. 



In the foregoing sketch an attempt has been made to indicate the methods which 



TRANS. ROY. SOC. EDIN., VOL. L, PART III (NO. 18). 79 



