644 DR JAMES W. DAWSON ON 



both of these points and also to Strumpell' s view that the vessels throughout the 

 body, not solely in the central nervous system, would be affected were it an 

 inflammatory process. But it may be stated here that Strumpell and Muller's 

 view of a "multiple gliosis" is scarcely tenable for the cortical areas, which 

 have been proved not to consist of proliferated glia fibrils, and for areas in the 

 peripheral nerves. The latter, however, if their existence can be demonstrated, 

 might well be analogous formations — consisting of a proliferated, interstitial tissue 

 whose origin is in the Schwann's sheath, in virtue of its ectodermal derivation 

 from the neural crest. 



From a comparison of the histological study with the above statements, it will be 

 seen that I am not in agreement with Muller's view that the areas in disseminated 

 sclerosis arise solely on the basis of an increasing glia hyperplasia, and that they can 

 be always separated from those arising on the basis of an inflammatory reaction. In 

 this study there is overwhelming evidence that the great majority of the areas have 

 arisen on an inflammatory basis and that a small minority have arisen on the former 

 basis. The end result of both is a tangle of glia fibres. During the process of the 

 gradually increasing glia hyperplasia it is possible, especially in the lateral columns 

 of the cord, to differentiate this mode of formation of a sclerosed area, and I relate 

 such not to a developmental defect of the glia, as Muller and Strumpell have 

 done, but to a special reaction in the glia, according to the nature and intensity of 

 the causal factor (see p. 666). We have therefore not two affections, or necessarily 

 different stages of the same process, but one causal factor which probably acts with 

 varying intensity. 



2. Inflammatory. 



Having therefore given adherence, on the grounds of an exhaustive study of nine 

 cases of disseminated sclerosis, to the inflammatory nature of the process underlying 

 this condition, it must now be considered briefly what is meant by inflammation in 

 the central nervous system. 



It is usual to classify the varying histological pictures in the processes termed 

 " inflammatory " in the central nervous system into parenchymatous and interstitial, 

 analogous to the processes in the glandular organs of the body. But the conception 

 of a purely parenchymatous inflammation in the central nervous system has little 

 anatomical support, for the evidence of changes of a regressive nature in the nerve 

 cells, axis cylinders, and myelin sheaths is accompanied by evidence of progressive 

 phenomena in the. other tissue elements. It is not possible, therefore, to draw any 

 clear distinction between simple tissue degeneration and inflammation, and it is 

 usual to designate as "myelitis" both the processes, which are from the beginning 

 distinguished by inflammatory exudations and cell infiltration, and those which begin 

 as degenerations and only in their further course are connected with pathological 

 exudation or proliferative processes. 



