THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 555 



not only axis cylinders deprived of their myelin sheath but also those " naked " axis 

 cylinders which no longer contain myelo-axostroma (a cement substance enclosing 

 and holding together the neurofibrils which, as its name indicates, histogenetically 

 and chemically resembles the myelin of the medullated sheath). The extreme 

 uncertainty of the Bielschowsky method and its various modifications has been 

 frequently emphasised. It is undoubtedly " a method full of surprises and dis- 

 appointments even for the experienced technician." In numerous instances the glia 

 fibrils are also stained, and as these run longitudinally in the same direction as the 

 axis cylinders the result is confusing ; at other times the medullated sheath is 

 stained — a point very forcibly brought out in comparing frozen sections stained with 

 iron-hsematoxylin. The method, however, often gives very serviceable, and even 

 beautiful, results, and is applicable to both celloidin and frozen sections, but one 

 must accept a negative picture with very great reserve. Two non-essential 

 modifications were adopted, both of which seemed to make the result less capricious. 

 The one, recommended by Schlemmer, has for its object the obtaining of an 

 ammoniated silver solution, of uniform strength, which will not become cloudy or 

 discoloured when exposed to light ; the other is an addition of a slight trace of 

 acetic acid to the alcohol in which the sections are immersed before being brought 

 into the ammoniated silver solution. 



A third specific staining method for axis cylinders was also tried : Strahuber's 

 aniline blue method, differentiating the sections with saturated sodium hypochlorite 

 solution. The aniline blue, however, while bringing out axis cylinders very 

 beautifully in normal tissues, distinguishes them very insufficiently from the glia 

 fibrils in sclerosed tissue. Strahuber's method stains only those axis cylinders 

 which still retain the myelo-axostroma, or as Strahuber named it, the chromatenin 

 or axo-chromatenin — terms which seemed to him to indicate that the material to 

 which it refers is only one of the constituents of the peri-fibrillar substance. 

 Fibres which have lost their myelin sheath are, therefore, merely non-myelinated 

 axis cylinders, not necessarily naked axis cylinders. 



Before leaving axis-cylinder methods, it must be mentioned that there is no 

 specific method analogous to that of Marchi to represent the degeneration of the 

 axis cylinder. Eosin and picro-fuchsin and several other stains frequently bring out 

 the axis cylinders very clearly, but they are not elective stains, and B artels states 

 that the homogeneous granular masses, which are recognisable in sclerosed areas by 

 means of the diffuse stains, are not seen with silver impregnation. 



Elective glia-staining methods still leave much to be desired. Virchow noted 

 the extreme susceptibility of the glia fibrils to post-mortem changes and the 

 necessity of bringing material into the fixing fluid fresh. The Weigert glia method, 

 to which we owe our present knowledge of the finer structure of the neuroglia both 

 in normal and pathological conditions, is very difficult to work, very capricious, and, 

 in particular, frequently fails in staining the cerebral cortex. Its success, too, is 



