524 DR JAMES W. DAWSON ON 



mental or congenital defect of the neuroglial or nervous tissue (perhaps similar to 

 or analogous to the gliomatosis in cases of syringomyelia) which renders it more 

 vulnerable or liable to be affected by irritation than the neuroglial or nervous tissue 

 of the normal individual." 



These views may be termed the exogenous and endogenous theories, using 

 these words in their strictest meaning. The former ascribes to disseminated 

 sclerosis an inflammatory process as its basis, and most observers accept the 

 inflammatory nature of the process in some form. The latter view, strongly 

 advocated by Strtjmpell and supported by Muller in his monograph, looks upon 

 disseminated sclerosis as a disease independent of external factors, except as " agents 

 provocateurs." Muller distinguishes between true or primary disseminated sclerosis, 

 a primary glia formation due to malformation of the glia — a disease sui generis — and 

 secondary disseminated sclerosis, a myelitic form, one of a community of allied 

 diseases. This standpoint, that a uniform explanation of all cases of disseminated 

 sclerosis cannot be given, is taken up by many recent writers. Others, however, 

 cannot recognise the existence of an acute or secondary disseminated sclerosis which 

 differs in its evolution from the chronic forms, but whose pathological anatomy is 

 yet almost identical. 



Concerning the origin, as concerning the nature of the process, the views are no 

 less divergent. Supporters of the endogenous theory see in disseminated sclerosis a 

 multiple gliosis whose origin is, naturally, in the neuroglia tissue. Supporters of 

 the inflammatory nature of the diseased process are, however, widely divided in 

 their views regarding its origin. In a sclerotic patch changes occur in the three 

 separate structural elements of the tissue : (l) the nervous elements — the myelin 

 sheath of the nerve fibre ; (2) the interstitial tissue — the glia ; and (3) the blood- 

 vessels. The differing views are related to these three components, and according 

 to the anatomical change most in evidence writers have ascribed the origin of the 

 process to a primary parenchymatous change, a primary interstitial process, or a 

 primary vessel alteration. We must undoubtedly differentiate three groups of 

 changes, and the question constantly arises, which is primary and are the others 

 secondary, i.e. are they so related as to be cause and effect, or are they together 

 due to the simultaneous action of the etiological factor ? Many neuro-pathologists 

 believe that here, as elsewhere, it is immaterial whether the reaction is discernible 

 first in the parenchyma, or interstitial tissue, or vessels. It may be assumed that 

 there are individual factors which, through the reaction of the tissues upon the 

 unknown, though probably toxic, stimulation of the three components, determine the 

 anatomical picture, allowing in one case one component and in another case another 

 component to come to the front. 



It is, therefore, clear that amongst the questions raised in any discussion 

 regarding the nature and origin of disseminated sclerosis are the following : — its 

 relation to acute, subacute, and chronic inflammatory processes in the central 



