THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 531 



blood-cells, partly adherent to the vessel walls and partly filling the vessel as 

 emboli. Kjbbert looked upon these as multiple thrombi, and thought that they 

 played an important role in the causation of the process, for in such thrombosed 

 areas arose the commencing emigration of leucocytes. He thought that the charac- 

 teristic form of the areas might well be accounted for by multiple emboli, and he 

 also related to the blood-vessels the fact that the cerebral areas so frequently reached 

 up to the cortex but did not involve it — explaining this circumstance by the few 

 anastomoses between the vessels of the white and grey matter. 



Eibbert thought that the exciting cause of the inflammation circulates in the 

 blood, and that owing to its presence a clot formed at some part of a small blood- 

 vessel. At this point an irritation of the vessel wall is set up with a peri-vascular 

 inflammation : this inflammation extends around the blood-vessel and invades the 

 surrounding tissues, causing degeneration of the nerve fibres and an active prolifera- 

 tion of the glia. The glia nuclei proliferate and form large cells with an abundant 

 protoplasm from which radiates the fibre-work of the glia. The fat granules, arising 

 from the degeneration of the myelin sheath," are taken up by the emigrated white 

 blood-cells and are carried to the lymph sheaths of the blood-vessels. The prolifer- 

 ated glia, after the removal of the fat, forms numerous fibrils, and thus arises 

 a dense grey sclerotic area in which the protoplasm even of the large nucleated 

 cells disappears. 



French writers support chiefly the vascular origin of disseminated sclerosis. 

 Amongst these may be mentioned the names of Dejerine and Pierre Marie. 



Dejerine (1884) maintained that the configuration and dissemination of the 

 areas could be explained only by relating them to changes in the blood-vessels. He 

 found the blood-vessels altered, with a peri-arteritis and their calibre diminished, 

 and that a vessel, thus changed, was the central point of each plaque. Dejerine 

 thought that the causal factor, a microbe or a humoral agent of undetermined 

 nature, circulated in the blood-vessels, modifying in some way their nutrition, and 

 that this was the primary change. The effect on the surrounding tissue is seen first 

 in the glia, which by its proliferation caused an " excentric compression of nerve 

 tubes," leading to their disappearance. 



Pierre Marie (1884-1895) has emphasised the special relation of disseminated 

 sclerosis to infectious diseases, especially enteric fever, pneumonia, scarlet fever, and 

 measles, and, of lesser importance, diphtheria, whooping-cough, erysipelas, dysentery, 

 and even cholera. Marie thinks that disseminated sclerosis is due, not to the 

 different micro-organisms which produce these diseases, but to a combined infection 

 occurring during their course. He suggests that the lesions in the brain and spinal 

 cord are probably due to an ordinary pathogenic microbe, whose special action is 

 due to its special localisation. The etiological influence of the infectious diseases is 

 such that there may result changes of the vessels, and the sclerotic areas are 

 therefore due to the localisation of infectious vessel disease in the central nervous 



