THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 687 



homogeneous " hyaline " change in which nothing can be recognised of specific 

 muscle, connective tissue, and elastic elements. 



(xvi) Fat granule cells (" Fettkornchenzellen " ). The first fat granule cells prob- 

 ably arise from the proliferation of the small round glia cells, and at a later stage, also 

 from a proliferation of the endothelial elements of the adventitia. They absorb the 

 degenerated myelin in the form possibly of a solution, which is precipitated as 

 granules in the protoplasmic substance of the cell : they pass, or are drawn in by 

 suction and the pressure of the increasing glia fibrils, into the lymphatic sheaths of 

 the capillaries and transition vessels, and thence by the larger vessels to the inner 

 layers of the pia. On their way large numbers are broken up in situ, and their 

 crenated nuclei can for a long time be recognised as one of the nuclear elements of 

 the adventitia. 



(xvii) The cranial and spinal nerve roots are frequently involved in the glious 

 portion of their extra-medullary course. Such changes, in the posterior spinal and 

 analogous nerve roots, may account for the existence of the sensory changes, which are 

 almost always present to a slight extent, and especially for the trigeminal neuralgia. 



(xviii) The meninges. The occasional variations in the meninges are related to com- 

 plications and are probably of no significance in the pathogenesis of the disease. 



Approximately final answers can, therefore, be given to the questions relating to 

 the nature of the process underlying disseminated sclerosis, to its origin, to the 

 relation of several secondary etiological factors, and to certain aspects of the mode 

 of action of the final causal agent. We are, however, still quite in the dark con- 

 cerning the nature of this final cause, which determines, anatomically, a process, 

 so well defined, and one without any close analogy ; and, clinically, a disease 

 which, however variable the early symptoms, conceals its characteristic course only 

 temporarily. The frequent presence of the cardinal symptoms, in spite of the seem- 

 ing irregularity and incidence in the position of the areas and their restriction, seems 

 to point to a certain constancy in the changes, the nature of which is not yet fully 

 known, but which may be dependent on the production of a specific metabolic 

 disturbance, due to a latent organism or an auto-toxin. All that is most important, 

 therefore, still remains for future investigations along bacteriological, serological, 

 and experimental lines, which have recently done so much to clear up the etiology 

 of other affections of the central nervous system. 



