THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 603 



How of lymph upwards along the nerves, the main current of which lies at the 

 periphery of the nerve immediately under the fibrous sheath. It was presumable, 

 therefore, that we ought to find in the cord of cases in which some septic focus 

 existed, e.g. bed-sores or an extensive pyelitis, lesions of the posterior columns, 

 caused by toxins ascending in the lymph stream. The evidence for this was care- 

 fully sought for, but the lesions were already so extensive — and the terminal infec- 

 tion, if this were the cause of the general myelin degeneration, affected the whole 

 transverse section, including the attached nerve roots — that no conclusion could be 

 come to on this point. 



Two points of interest may be added : (l) that the intra-medullary portions of 

 both anterior and posterior nerve roots seemed frequently to withstand the sclerotic 

 process much longer than the white matter through which they passed, and (2) 

 fig. 250 indicates how normal nerve roots may be attached to a segment of the cord 

 entirely deprived of myelin, and figs. 452, 453 that a similar condition of the nerve 

 bundles of the cauda equina may exist though the whole lumbo-sacral cord shows, 

 in Weigert sections, complete sclerosis. In both the longitudinal section (fig. 90) 

 and at every level of the cord from which fig. 92 was taken, Bielschowsky prepara- 

 tions showed an almost normal number of retained axis cylinders (fig. 427). The 

 posterior root ganglia related to numerous segments were investigated. 



In only one case (L. W.) were the peripheral nerves examined. In both Marchi 

 and Weigert preparations, both transverse and longitudinal, from two levels, at least 

 5 centimetres distant from each other, showed a complete absence of early or late 

 degeneration in the following nerves : popliteal, peroneal, and median on both sides, 

 and the right sciatic (fig. 454). In the left sciatic nerve, however, there was a 

 distinct Marchi degeneration (fig. 324). 



(c) Changes in the Meninges. 



Borst has described, in all the four cases examined by him, adhesions and 

 thickenings of the cerebral and spinal cord membranes. The significance ascribed 

 by him to these changes is of great importance in relation to the pathogenesis of 

 disseminated sclerosis, and this subject will be more fully dealt with when con- 

 sidering general changes in the lymphatics. A few histological details may, however, 

 be given here. In uncomplicated cases the meninges were found almost normal : 

 the pia was frequently slightly thickened, contained a slight increase of cells, and 

 the pial vessels showed changes very similar to those within the sclerosed tissue. 

 In the earlier stages the vessel walls and inner layers of the pia contained fat granule 

 cells. In other cases, however, the cerebral and spinal soft meninges were infiltrated 

 with cells, chiefly lymphocytes, and a few plasma cells, which also passed in with 

 the vessels into the substance of the cord. Many dense glia fibres — radiating from 

 the glia marginal zone into the pia — were found around the venous vessels as they 

 passed out of the cord, and also around these vessels there was a marked accumula- 



