THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 601 



4. Changes in Nerve Roots and Meninges. 



(a) Optic Nerve. 



The optic nerve and olfactory lobe must, embryologically, be looked upon as 

 parts of the central nervous system. They therefore contain neuroglia, and must 

 be considered apart from the other cranial nerve roots. The olfactory lobe was 

 examined in only two of the cases : both peduncle and lobe in each case showed 

 distinct signs of demyelination. Owing to the extreme flattening of the tissue before 

 embedding, it was found impossible to get very satisfactory preparations, and only 

 Weigert and Van Gieson stained sections were examined. 



The optic nerve, chiasma, and anterior portion of the tract, investigated in seven 

 of the cases by numerous staining methods, in every instance showed marked 

 involvement. In one case Weigert sections, both longitudinal and transverse, 

 showed complete absence of myelin in the whole of the intra-cranial course of both 

 optic nerves, and the chiasma was similarly degenerated. Figs. 64, 65 ; 100, 101 ; 

 163, 165 ; 225 ; 431, 432 ; 444 show the degree of myelin involvement in six separate 

 cases : the chiasma, as will be seen, was the site most frequently affected, and the 

 first evidences were manifested in its anterior border. In one case the optic tract 

 on both sides was cut in celloidin sections from the chiasma to the corpora geniculata 

 interna, and both showed a very characteristic discontinuous degeneration : the 

 degeneration in the chiasma passed into both optic tracts and then ceased — to begin 

 again at a point midway in its course. Weigert counter-stained sections brought 

 out very beautifully the advanced septal and blood-vessel change which accompanied 

 the sclerosis in the optic nerves (fig. 444). Van Gieson sections showed that this had 

 commenced in a proliferation of the fine connective tissue elements between the nerve 

 fibres, and that this active proliferative process had then extended to the larger 

 septa and the inner layers of the optic sheaths. The glia elements had shared in 

 this reaction, and there resulted rows of large protoplasmic glia cells with long 

 branching processes. Later, the glia fibril formation seemed almost masked by the 

 great connective tissue increase, which the very numerous blood-vessels of the septa 

 had shared. The degeneration of the myelin sheath appears to take place very 

 rapidly, and long tubular rows of fat granule cells are found in Marchi sections 

 (figs. 64, 65) : the mode of their removal in the blood-vessel lymphatics is in every 

 way comparable to that in the central nervous tissue. Redlich and others have 

 noted the long persistence of the axis cylinders in the optic nerve sclerosis. In one 

 case, macroscopically, there was very evident involvement of the optic chiasma and 

 nerves : they presented a completely gelatinous, almost transparent, appearance, and 

 yet Cajal-stained sections showed an almost complete preservation of the axis 

 cylinders in nerves, chiasma, and tract (figs. 431, 432). 



The characteristics of the areas in the optic nerves and chiasma are therefore 

 related to the presence of both glia and connective tissue interstitial elements, for 



