THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 593 



As the glia reticulum becomes denser and encroaches more and more on the 

 ganglion cell processes and cell body, there takes place a gradual atrophy of the cell 

 (fig. 415). For a long time an atrophic, rounded or oval cell, with no processes and 

 no chromatophile granules and usually without nucleus, may be recognised (fig. 418). 

 But gradually this faintly or diffusely staining body can no longer be recognised as a 

 cell, and this dense tissue consists of the deeply-staining glia nuclei and the abundant 

 delicate fibrils (fig. 419). 



It is frequently stated that sclerotic areas are never found solely in the grey 

 matter, but that these are always extensions from sclerosis of the white columns. 

 In serial sections, however, it could be proved that small sclerotic areas may be 

 confined, throughout their whole longitudinal extent, to the grey matter. An 

 affection of the myelin reticulum around and between one or other group of cells 

 (figs. 137 and 155) has frequently been the sole trace of demyelination in many 

 sections of the lumbar cord. A peri-central sclerosis (fig. 197), limited at first 

 entirely to the commissures, is often the starting-point of an extension into each 

 anterior and lateral horn. The spread may take place forwards along each lateral 

 margin of the anterior fissure or posteriorly along the posterior median septum as a 

 central line, or the extension may be along all of these planes, giving rise to a 

 cruciform area of sclerosis, which in its further extension may involve the whole 

 transverse section, leaving sometimes four lateral and symmetrical peripheral 

 areas situated near the posterior and anterior roots respectively (fig. 210). 



Undoubtedly, however, the affection of the anterior horn of grey matter of the 

 cord starts very frequently from the extension inwards of an area of sclerosis situated 

 at the margin between white and grey matter (fig. 241). In the transition of an 

 area from grey to white there is such marked glia proliferation that the transition 

 can no longer be recognised. Muller looks upon this border line as an area in 

 which the glia is more fully developed : this is certainly so in the region of the 

 formatio reticularis, which is the most frequent site of development of a gradually 

 increasing glia hyperplasia. The development of areas at this transition zone has 

 been explained by other writers with reference to the breaking up of both central 

 and peripheral vessels, and it is not difficult to trace the direct passage of a lateral 

 vessel to such an area (figs. 241 and 253), or of thickened commissural branches 

 passing to areas in the lateral and anterior grey matter. 



The definition of the area in the grey matter was never a sharp one : the nerve 

 fibres of the reticulum passing into the area for very varying distances (fig. 412). 

 It was also found that where an areolar zone surrounded an area which involved both 

 white and grey matter, it ceased almost abruptly at the transition and was never 

 present in the grey matter. 



When sclerosis affects the cranial nuclei, as is so frequently the case, the process 

 may again be confined to the grey matter, but this is rare, and it is much more often 

 an extension of a process which involves the floor of the IVth ventricle. The 



