THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 527 



Classification : — 



(1) Inflammatory nature of the process : — 



A. Primary change in the neuroglia. 



B. Primary change in the parenchyma. 



C. Primary change in the blood-vessels. 



D. Disturbances in the lymph circulation. 



(2) Developmental nature of the process : — 



A. Deficient " Anlage " of the nerve elements. 



B. Multiple gliosis. 



(3) More recent researches, 1903-1913. 



(l) Inflammatory Nature of the Process. 



The views as to the inflammatory nature of the process are related to considera- 

 tions regarding primary changes in the glia, the true nervous elements, and the 

 blood-vessels. The final etiological factor or factors which bring the primary change 

 into operation have, as yet, received no satisfactory explanation, but it is agreed 

 that the postulated virus circulates in the blood-vessels or lymphatics and exerts 

 its action primarily on the glia, the myelin sheath of the nerve fibre, or the blood- 

 vessel wall itself. 



A. Primary Change in the Glia. 



According to the writers who support this view, the morbid process starts in a 

 formative irritation of the glia, comparable to a chronic interstitial inflammation in 

 other organs, e.g. liver or kidney. The thickening of the glia reticulum and the 

 formation of the glia fibrils strangle, as it were, the myelin sheath of the nerve 

 fibres, which gradually diminish in volume and then disappear, leaving the axis 

 cylinders persisting for a long time. 



Charcot (1866) and his followers held firmly to this view : they regarded the 

 changes in the nerve fibres as secondary to the glia proliferation and the changes in 

 the blood-vessels as a much later and not an essential part of the process. Charcot 

 looked upon the neuroglia as a reticulated connective tissue, the meshes of which 

 contained one or more nerve fibres. In the grey matter the meshes were much 

 smaller than in the white, and in both the network served as a framework for the 

 blood-vessels. At the nodal points of the reticulum were situated the neuroglia 

 nuclei with a thin layer of protoplasm and numerous processes of different lengths. 

 These processes seemed to unite with the trabeculse of the reticulum, which continue 

 them, as it were, without any line of demarcation. In his description of the 

 topographical distribution of the areas he noted the frequent peri-ventricular 

 localisation, that the spinal and cranial nerve roots were frequently affected, and 

 that the dorsal sections of the medulla oblongata, where the cranial nuclei lie, show 



