620 DR JAMES W. DAWSON ON 



the cord, or bowl-shaped (fig. 257). When a large part of the peripheral portion of 

 the cord was affected, perhaps through fusion of contiguous lateral areas, the sclerosis 

 frequently mapped out the triangular portion between anterior and posterior root 

 entry zones and extended inwards to involve the grey matter — the base of this 

 triangle being sub-pial (fig. 246). The areas within the white matter of the lateral 

 columns were frequently round or oval (figs. 256, 258) and often occupied the region 

 of the crossed pyramidal tracts. In the posterior columns the areas assume specially 

 an elongated oval shape (figs. 194, 261), the long diameter of which is pointed sagit- 

 tally. The centre line of this oval may be either the posterior median septum or the 

 paramedian septum : in its extension the involvement of the columns is often uni- 

 form, but occasionally more on one side than another (fig. 259). When the ventral 

 portion of the posterior columns is affected by a small, isolated area, it has usually a 

 more or less triangular form, with the base to the posterior commissure (fig. 260). 

 In its extension such an area involves both posterior horns, and may pass backwards 

 on both sides of the median septum- — the apex gradually approaching the periphery, 

 but often leaving symmetrical islets of normal tissue in the angles near the posterior 

 root entry zones on either side. 



Isolated areas may occur in the grey matter of the cord, especially in the anterior 

 horns. Such areas may apparently involve one group of nerve cells (figs. 234, 243), 

 or may, rarely, map out the whole of one horn as a demyelinated area before it 

 extends into the white matter (fig. 199). The most frequent involvement, however, 

 of the grey matter is a peri-central sclerosis (figs. 197-199), which may be very 

 marked at almost every level of the cord. In its extension this may pass anteriorly 

 or laterally into the grey matter or directly anterior or posterior along both sides of 

 the anterior and posterior fissures, or both or all combined, so that in its further 

 extension it involves almost the whole transverse section of the cord. The 

 symmetry of such involvement is often very marked (fig. 247), and is never more 

 clearly brought out than where isolated islets of myelinated fibres are left- at corre- 

 sponding marginal parts of an otherwise demyelinated transection (fig. 210). Similar 

 marginal areas in the region of the cerebellar tracts are also frequently left after an 

 apparently symmetrical involvement of the lateral columns and adjoining portions 

 of the grey matter. 



The longitudinal extension of areas within the white matter is very varied, but 

 sometimes reaches over several segments. Their form is usually an elongated oval, 

 or a series of elongated oval areas have seemed to join on to one another at their 

 adjacent ends (figs. 30-31). In the frontal longitudinal section of an isolated area 

 in the posterior columns, it is possible to recognise how the numerous vertical 

 branches of a vessel system are all involved and not one primary vessel stem. Very 

 numerous segments were cut in serial longitudinal sections, both in frontal and 

 sagittal direction. In some of these only traces of myelinated fibres could be found 

 along the margins throughout the whole segment : in others, the primary oval area 



