THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 575 



method) ; and, finally, a nucleated transition zone, which gives frequently an abrupt 

 passage to normal tissue. On the other hand, the recent areas, while presenting 

 a striking contrast to the former, have also some of these characteristics, but in 

 a lesser or different degree : the absence of myelin within the area ; a very 

 slight commencing glia fibril formation, but a very intensive glia cell prolifera- 

 tion ; the persistence, to a much less extent, of axis cylinders and those per- 

 sisting being markedly altered ; the presence of numerous dilated blood-vessels 

 with nucleated elements in their adventitial spaces ; the marked indications of 

 a previous myelin degeneration in the presence of fat granule cells which fill up 

 all the interstices of the tissue and the adventitial lymph spaces of the blood- 

 vessels ; and, finally, a very gradual nucleated transition zone in which all these 

 changes are less marked, but are combined with an evident degeneration of the 

 myelin of the nerve fibres in this zone. 



The question naturally arises : What relation do these two types of areas bear 

 to one another ? The finding of both types side by side in the same case, and the 

 clinical history — with its remissions and relapses — argue for a close connection 

 between them. Yet numerous writers, while not denying that the end result of 

 the recent areas is a sclerotic tissue which bears a close agreement to the old 

 sclerotic areas typical of the disease first designated by Charcot disseminated 

 sclerosis, claim that true or primary disseminated sclerosis arises solely on the basis 

 of areas of the first type, in whose evolution there is no stage corresponding to 

 that of " fat granular cell myelitis." Areas of sclerosis which pass through the 

 stage of the second type must be designated as secondary sclerosis, and those 

 areas arise on the basis of a disseminated myelitis. 



The questions must then arise : What is the evolution of the first type ? and 

 what are the stages in the evolution of the so-called secondary sclerosis ? In the 

 next two sections an endeavour will be made to trace their respective evolution. 



3. Evolution of an Actual Sclerotic Area. 



A. Through Stages of increasing Glia Hyperplasia. 



The supporters of the view of a primary form of disseminated sclerosis claim 

 that the essential lesion lies in the neuroglia tissue. By some anomaly of develop- 

 ment this tissue, in certain areas, undergoes an intensive proliferation, which, by a 

 gradual constriction of the glia meshes, produces a slow atrophy of the myelin 

 sheath of the nerve fibre. The myelinated nerve fibre, therefore, in certain areas, 

 undergoes a progressive reduction in its volume till it is completely replaced by 

 the glia fibril proliferation, leaving the axis cylinder preserved. This proliferation 

 goes a stage further than a mere substitution of glia fibrils for myelin sheath, for 

 it is of such intensity that in no other condition is the glia proliferation so marked 

 as in disseminated sclerosis (Weigert). It is claimed that not only is there a 



