THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 521 



themselves. Nissl laid stress on the fact that practical neuropathology can and 

 must be pursued without regard to definite ideas as to the functional significance 

 of the individual component parts of the tissue. He pointed out that it is sufficient 

 in the first place to collect pathological data regarding definite diseased conditions, 

 and that for that purpose the changes in the supporting tissue — the glia and the 

 vascular connective tissue — may be of greater importance and much more really 

 decisive than the changes in the specific tissue elements — the nerve cells and nerve 

 fibres— which are yet of greater functional importance. The classical methods of 

 Marchi for early, and of Weigert for late, fibre tract degeneration have, therefore, 

 been supplemented by modern specific and diffuse staining methods. The examina- 

 tion of small sections for the recognition of these finer histological details has, on the 

 other hand, been supplemented by large brain sections through the whole hemisphere. 

 These sections, stained with Weigert's myelin sheath stain and a diffuse cell stain, 

 give a very instructive comparative representation of the gyri and their associated 

 sulci, and an idea of the extension of the process. 



The pathological process may be disseminated through brain, pons, medulla 

 oblongata, and spinal cord, and may produce symptoms of a very diverse character. 

 The possibility of any useful clinical classification is, therefore, very slight, and an 

 anatomical basis has been adopted for the classification of the various clinical types. 

 According to the predominance of the symptoms, the disease has been divided 

 clinically into cerebral, spinal, and cerebro-spinal forms, and the different possi- 

 bilities of anatomical distribution and localisation have led to a similar patho- 

 logical classification. Probably no cases are purely of one type, and experience has 

 shown that, if sufficiently careful search is made, sclerotic areas will be found in 

 nearly all cases distributed through both brain and cord, though perhaps much 

 more marked in one or other position. As far as we know from the findings in 

 other organs of the body, there is no widespread reaction to the etiological factor, 

 such as is found in acute poliomyelitis. The anatomical findings point to a process 

 localised in the central nervous system. 



Before referring to some of the problems met with in the study of disseminated 

 sclerosis, it will be convenient to give an indication of the pathological changes 

 found in a well-marked case of the disease. Williamson (1908) in his text-book 

 gives a brief, clear description of the main features of the pathological anatomy, 

 from which we take the following detached statements : — 



" The pathological examination of the nervous system reveals patches of sclerosis 

 scattered about in the most irregular manner in the brain, pons, medulla, and 

 spinal cord. Both white and grey matter may be affected, though the former is 

 more frequently the seat of the disease. The patches are in some cases grey in 

 colour and sharply defined ; in others greyish white and less sharply defined. Large 

 patches in the cord, medulla, and pons may extend over the greater part of the 

 transverse section. The largest patches are seen in the white matter of the brain. 



