THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 609 



(fig. 386), but show chromatolysis and have their dendrites thickened or weakly- 

 stained or absent, and the cell contour is rounded or pear-shaped (fig. 22). These 

 changes involve not only the demyelinated area but also the adjoining stretches of 

 the cortex to a varying extent. But the most characteristic appearance in a cortical 

 area, and that which enables it, under low power, to be readily recognised, is the 

 nuclear increase around the ganglion cells. The majority of the ganglion cells, in 

 the lower layers of the cortex and in the layer of the large pyramids, are surrounded 

 by small nests of cells (figs. 381, 393), from five to ten in number. These with 

 diffuse stains have a small deeply-staining nucleus with little protoplasm, and cause, 

 according to their number and arrangement, more or less deformity and atrophy of 

 the ganglion cell, but we have never seen the penetration of such cells into the 

 ganglion cell body. They have probably arisen from the pre-existing satellite cells, 

 and their proliferation is taken as an indication of the inter-relation between ganglion 

 cell and its satellite cells (" Trabantzellen "). Marinesco thinks that in health the 

 former secrete substances which exercise a controlling influence on the size and 

 development of the latter : if any noxious or toxic agent affects the former, this con- 

 trolling secretion is diminished in quantity and quality, and the neuroglia cells react 

 accordingly by increasing in size and numbers. This change is again not limited to 

 the demyelinated areas, but passes over to the adjoining stretches of the cortex. 



Comparatively little change was found in the cells of the posterior root ganglia 

 (fig. 420). Those that were present indicated a general reaction, probably in no way 

 related to the sclerotic process in the cord. 



3. Neuroglia. 



The changes in the neuroglia represent, in the opinion of numerous observers, the 

 dominant and essential histological feature of disseminated sclerosis. Whilst the 

 changes in the nerve fibres show little variation in the individual cases, the glia 

 components show wide differences. In an early area we have seen that the most 

 important and characteristic finding is the enormous number of large cell elements 

 (fig. 380) which in their further evolution are transformed into glia fibrils (fig. 384) 

 and glia nuclei. In an actual sclerotic area we have a dense glia fibril mass, appar- 

 ently without spaces (figs. 354, 364). The histological characters of the glia, there- 

 fore, depend on the length and the intensity of the process. In the final result the 

 name " sclerosis " is justified by the amount of neuroglia present in the areas, and 

 Weigert has stated that the glia hyperplasia is greater here than in any other form 

 of sclerosis. The neuroglia, though not from a histogenetic, yet from a morphological 

 and biological standpoint, may be looked upon as a true fibrous connective tissue. 

 It is thus of great significance that the glia begins to proliferate when component 

 parts of the specific nervous tissue are destroyed, even where any stimulus capable of 

 causing primary proliferation is absent. The classical example of this is the secondary 

 degeneration of the white substance, where the secondary glia proliferation sets in 



