630 DR JAMES W. DAWSON ON 



the sclerosis extends into the white matter of the cerebellum, the remaining white 

 matter of which also shows numerous irregular patches in early stages. Several of 

 the cores of the folise are also cut across by other small areas. 



Middle of the pons (fig. 41). — At this level the one middle peduncle is still involved 

 by a large irregular area, which extends from ventricle to surface and involves most 

 of the pyramidal fibres, the transverse fibres, the trapezoid fibres, the superior olive 

 and associated nuclei, together with the nuclei around the IVth ventricle. On the 

 opposite side the sclerosis of the middle peduncle is not so complete : one patch 

 extends inwards from the surface and affects the outer pyramidal fibres, but does not 

 extend further than the inner border of the trapezium. The floor, angle, and roof of 

 the ventricle are also involved, and on this side two further areas occur — one 

 destroying the superior olive, the other the trapezoidal and middle peduncle fibres ; 

 while a central area involves the trapezium again and the adjoining portions of 

 the formatio reticularis. 



Upper part of middle peduncles (fig. 42). — Here the aqueduct of Sylvius is 

 surrounded by a well-marked ring of sclerosis, which extends to the surface, allowing 

 only a few fibres of the superior cerebellar peduncles on each side to escape. On the 

 one side this area extends laterally into the middle peduncle, almost completely 

 obliterating it and sending a tongue-like projection into the fibres of the trapezium. 

 On the other side the anterior third of the middle peduncle is affected, and the 

 sclerosis extends postero-mesially and involves the grey matter of the pons, the 

 corresponding fibres, and the middle of the pyramids. 



Upper pons (fig. 43). — The ring round the aqueduct of Sylvius is now slightly 

 altered ; the greater part of one superior cerebellar peduncle escapes, while the 

 anterior part of the opposite peduncle is also free. The sclerosis extends laterally, 

 and is continuous on the one side with a large area involving the middle peduncle. 

 Three further sclerosed areas are found : one in the middle line involving the pontine 

 grey matter and fibres, and irregularly-shaped, almost symmetrical areas which 

 extend postero-mesially from the lateral side of the pyramidal fibres on each side 

 and involve two-thirds of their fibres with the corresponding connections. 



At a slightly higher level the central oval area increases in size, while the sclerosis 

 round the aqueduct diminishes, and is localised to one side. 



Junction of Pons and Mid-Brain (fig. 44). 



Three irregular areas here extend backwards from the surface of the pons. One, 

 in the mesial line, reaches almost to the mesial fillet. This area cuts across, in 

 irregularly-shaped, sharply-defined lines, the intersecting fibres of the raphe and the 

 adjoining fibres on each side. The other areas, also irregular in outline, pass back- 

 wards on each side of the pyramidal bundles, which are also partly involved. A 

 fourth patch extends forwards, from the aqueduct of Sylvius, in the middle line and 

 involves the posterior longitudinal bundle and the cells in the adjoining grey matter. 



