754 DR ALEXANDER BRUCE AND DR JAMES W. DAWSON ON 
The pial fibres could thus be stated to arise from the region of the anterior roots 
and most probably only from their immediate vicinity. They then pass rapidly, 
laterally or medially, and during their transition undergo a change in disposition and 
structure. Becoming more closely intertwined, by the time they have reached the 
mid-point of the lateral surface they have assumed a nodule formation. The fibres 
passing ventrally seldom assume this compact form till they emerge from the base of 
the anterior fissure, but in the region of the central canal they often form a large, dense 
nodule (fig. 44). As the fibres pass from the region of the anterior roots they become 
finer, stain less intensely, and show a very distinct segmental structure, the segments 
being in the form of bulging cylinders or varicosities with connecting bridges (fig. 13). 
The very fine character of the fibres around the vessels at the base of the anterior 
fissure is well brought out in fig. 42, where the central vessel is seen dividing, and the 
fibres pass in later sections along commissural vessels into the grey matter of either 
side, and along the branches to the anterior (fig. 41) and lateral (fig. 43) horns as 
leashes of fine fibrils. 
The fibres do not always pass to the base of the anterior fissure, but sometimes in- 
wards along the lateral branches of the anterior fissure vessels. Fig. 40 shows a 
wedge-shaped mass of fibres passing into the direct pyramidal tract near its anterior 
mesial margin. These fibres could be traced along this vessel, ultimately to form the 
nodule (fig. 27). This nodule, when traced downwards, broke up into strands of fibres 
in the meshwork of the grey matter. 
The fibres passing laterally in the pia could be traced passing inwards along almost 
every lateral vessel between anterior and posterior roots. If one section were taken 
and attention were concentrated on a strand of pial fibres in relation to the anterior 
roots, in successive sections that bundle could be followed as has been done above. 
Simultaneously, moreover, new bundles rise in their place cut transversely or longi- 
tudinally, and these, in their turn, can be followed to lateral vessels of the cord. We 
thus frequently get a radiation of the fine fibres in the peripheral vessels, or indications, 
marked by a fibrosis of the vessels, that such fibres have been present. The impression 
is given that if we could restore the picture to an earlier stage intra-medullary fibres 
in bundles or nodules would radiate inwards along all the lateral vessels to the 
circumference of the grey matter. 
The pial fibres, passing inwards along peripheral vessels, result in the formation, 
speaking generally, of nodules within the white matter, and these, running horizontally, 
have their greatest diameter in transverse sections of the cord (fig. 35). The fibres 
passing along central vessels form nodules in the grey matter, and these have their long 
axis more oblique or parallel to the long axis of the cord (fig. 29). Strands of fibres 
also in the pia cut longitudinally when traced upwards frequently become more oblique 
or longitudinal as they reach the anterior roots. 
The fibres of the nodules in relation to central and peripheral vessels frequently 
intermingle. As a rule by this time a very large nodule has formed at the base of the 
