678 DR JAMES W. DAWSON ON 



therefore, legitimate to assume that the varying picture is dependent upon certain 

 principles which enable us to recognise different degrees of one process rather than 

 several independent reactions. 



It is necessary, at the risk of complicating this argument, to mention one further 

 point. The anatomical expression of a "remission" must naturally be the gradual 

 clearing up of the cell exudation, and a sclerosing of the tissue with a retention of 

 the axis cylinders. The anatomical expression of a relapse is the presence of " early" 

 areas, so that the presence of areas in different stages of development is characteristic 

 of the anatomical picture of disseminated sclerosis. Now it is conceivable that a 

 disseminated myelo-encephalitis due, for example, to the direct toxi-infective agents 

 of the acute infectious diseases might run a slow course — healing slowly, and if death 

 resulted at this stage, the anatomical picture would show some areas actually 

 sclerosed, or at least with no trace of an existing process, and others in which such 

 traces were still left. It is evident that such an anatomical picture would be difficult 

 to separate from that of disseminated sclerosis, and that the long clinical course 

 would simulate a case of disseminated sclerosis with no true remissions. It is still 

 further necessary to refer to cases of so-called " acute multiple sclerosis." Such cases 

 are very difficult to classify : up to a certain point they resemble disseminated 

 sclerosis in virtue of their being disseminated affections of the central nervous system ; 

 but the criteria which give its characteristic course to disseminated sclerosis have 

 not had time to evolve. As the pathological data, however, resemble those of a 

 subacute process, with retention of axis cylinders, it might reasonably be admitted 

 that such cases are true disseminated sclerosis, which, from the importance of the 

 position of the earlier areas involved or other causes, have led to an acute course of 

 the disease and death. 



I therefore divide disseminated affections of the central nervous system into 

 (l) disseminated sclerosis — a subacute encephalo-myelitis, a condition which runs a 

 characteristic course with remissions and relapses, and (2) other disseminated affec- 

 tions. The only member of this group which presents real difficulties in clinical and 

 anatomical diagnosis is that due to acute disseminated myelo-encephalitis. In this 

 case the pathological and clinical concepts of the two diseases pass into each other : 

 the differential diagnosis must rest, clinically, on the further course of the disease, 

 and anatomically on data which differ only in degree. 



(iii) It is concluded, therefore, that there is much to favour the view that true 

 disseminated sclerosis is due to a specific morbid agent which calls forth a clearly- 

 defined clinical and anatomical picture : that other disseminated affections of the 

 central nervous system, such as disseminated arterio-sclerotic, syphilitic endarteritic, 

 and acute encephalo-myelitic processes may all produce a symptom-complex very 

 similar to that of disseminated sclerosis, but that they, in their further course, differ 

 from the latter in the characteristic remissions and relapses ; and further, that acute 

 infective diseases, trauma, chill, shock, and all known exogenous factors may act as 



