692 DR JAMES W. DAWSON ON 



and fairly large : on the left there is one very large dense area surrounded by a more diffuse 

 shadow sclerosis, which extends to the margin of the folise of the cerebellum. 



Upper Pons (figs. 79-80). — The peri-ventricular tissue is again very involved on all 

 sides. A few fibres stain darkly in the anterior medullary velum, which is otherwise involved. 

 The posterior third of one superior cerebellar peduncle is sclerosed, together with a narrow 

 band on the surface. Both superior longitudinal fasciculi are demyelinated and a bulb- 

 shaped projection passes laterally from them into one formatio reticularis. The opposite 

 superior cerebellar peduncle shows a broad band of sclerosis which extends forwards to the 

 anterior margin of the middle peduncle, thus involving some of the deep fibres of the Vth 

 nerve, the lateral fillet, the tract of Gowers, and adjoining fibres of the formatio reticularis 

 and middle pontine fibres. On the opposite side a broader and more irregular band com- 

 pletely cuts across the middle peduncles and some of the fibres of the Vth nerve, and con- 

 tinuous with this broad zone a projection passes into the formatio reticularis. On the 

 anterior surface of the pons three smaller, flattened, oval areas are present, one close to the 

 middle line and the other two on either side of it. A large number of very minute areas 

 are to be found involving individual bundles of the transverse fibres and the associated 

 nuclei, or bundles of the pyramidal tracts. 



At the level of the decussation of the superior cerebellar peduncles (fig. 81) the sclerosis 

 around the aqueduct of Sylvius is very well developed, but one of the posterior longitudinal 

 fasciculi has completely escaped and stands out clearly in the sclerotic tissue. From the 

 peri-central sclerosis a narrow band passes forwards in the middle line expanding suddenly 

 to a large bulbous extremity which obliterates the decussating fibres of the superior cere- 

 bellar peduncles. Small areas are found on both sides lateral to the superior cerebellar 

 peduncles, and several small areas are found on the surface just posterior to the transverse 

 fibres of the pons. 



Mid-Brain (fig. 82). — Around the aqueduct of Sylvius a broad zone of sclerosis extends 

 into the surrounding tissue on all sides, involving most of the structure of the tegmentum. 

 The lateral margins of the corpora quadrigemina stain normally, but both third nuclei are 

 lost. The adjacent fibres of the Illrd nerves and adjacent parts of both red nuclei are also 

 affected, and in addition several small, round areas are present in the substance of the red 

 nucleus on both sides. Early shadow sclerosis is seen in both substantia nigra, but both 

 crura are unaffected except for a slight early sclerosis close to the lateral sulcus. 



Cerebral Hemispheres. — (1) Section through the middle of the basal ganglia (figs. 70-71): 

 at this level the peri-ventricular sclerosis is the dominant feature. This is most marked 

 around the posterior horns of the lateral ventricle and along the sides of the optic thalamus. 



On the right side a dense irregular zone of sclerosis is present along the whole lateral 

 wall of the ventricle, and at the apex of the posterior horn this extends as a roughly quadri- 

 lateral area into the adjacent white matter, cutting across the tapetum, the optic radiations, 

 and inferior longitudinal bundle. The involvement of the anterior horn is limited to a few 

 small areas in the immediate white matter : this sclerosis is separated from the ventricle 

 by a narrow band of normal tissue. The surface of the right optic thalamus is irregularly 

 attacked. Dense areas occur at its anterior and posterior borders, with earlier areas between 

 them, and from the middle areas sclerotic tissue extends into the substance of the thalamus. 

 One large defined patch, roughly triangular, occurs just between the optic thalamus and 

 the lenticular nucleus, involving part of the genu of the internal capsule. A smaller round 

 area involves the retro-lenticular portion of the internal capsule. Two small areas are 

 present in the claustrum, and sclerotic tissue extends from these areas into the medullary 

 rays of the convolutions of the island of Reil. The convolutions of the parietal operculum 

 show extensive involvement both of the medullary rays and grey matter, and similar areas 

 occur in the white matter of the frontal operculum. The parietal and occipital lobes both 

 show numerous areas : some of these are limited to the white matter, others occupy the 



