THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 691 



side of the anterior median fissure, and this area of normal tissue on one side includes a 

 portion of the grey matter. This triangular area on both sides extends into Dl, but is 

 diminished in size and is soon lost. Small symmetrical groups of normal fibres are here 

 found at the tip of both posterior horns. In the upper dorsal region the normal fibres are 

 found in three isolated triangular groups. Such small triangular groups of normal but 

 faintly-staining fibres are found at numerous levels of both the lower dorsal and lumbar 

 cord. The sacral region shows the same extreme involvement. 



Medulla Oblongata. — Absent in Weigert sections. 



Pons Varolii. — Lower Third (fig. 76). — The distribution of the sclerosis is most irregular 

 and is especially developed around the floor and roof of the IVth ventricle. The whole 

 of the floor of the ventricle is affected, with the exception of a small band at the median 

 raphe, which includes the posterior longitudinal fasciculus. On the one side the sclerosed 

 tissue forms a large triangular area, the base of which extends from the median raphe to the 

 angle of the ventricle, and the apex reaches as far forwards as the tranverse fibres of the 

 pons. It thus completely blocks out the whole of the corresponding restiform body, and 

 as it extends around the angle of the ventricle, the nuclei of Deiters and of Bechterew cannot 

 be distinguished. The Vlllth nerve passes into this area of sclerosis : the nucleus of the 

 Vlth nerve and part of the Vllth are also involved in this area. Close to this larger area 

 are three smaller ones, one of which exactly picks out the superior olive, the second lies 

 between this and the lateral fillet, and the third lies in the formatio reticularis. Several 

 small or oval areas are present amongst the transverse fibres of the pons. On the opposite 

 side a tongue-like projection is seen extending from the floor of the IVth ventricle along 

 the mesial side of the restiform body ; this involves the spinal root of the Vth nerve, and 

 a part of the ventral cochlear nucleus. A small dense area and several early areas are 

 present in the restiform body. Two further small areas lie on the surface of the pons, one 

 just mesial to the entering fibres of the vTIIth nerve, and one at the level of the anterior 

 margin of the pyramids. The lateral walls and roof of the IVth ventricle are extensively 

 affected, and a sharply-outlined area obliterates the posterior portion of the dentate nucleus 

 on the right side. In front of this nucleus, in the white matter of the cerebellum, lies a 

 small area surrounded by a zone of faintly-staining tissue, also with a sharp outline. 

 A large diffuse early area is also found in the opposite central white matter of the cerebellum. 



Middle Third of Pons (fig. 77). — The peri-ventricular involvement on all sides is very 

 striking. The whole of the floor of the ventricle is sclerosed, and six irregular sclerotic pro- 

 jections pass ventrally from this base line. The sclerosis extends laterally around the 

 angles of the ventricle : on the right side the dentate nucleus escapes, but the white matter 

 adjoining contains two rounded areas, each with a zone of shadow sclerosis : on the left 

 side the dentate nucleus contains two early areas, the anterior of which is continuous with 

 the sclerosis of the angle of the ventricle. Several large and small early areas are found in 

 the central white matter of the cerebellum, and the white matter of the flocculi is also affected. 

 In a section at a higher level (fig. 78) the peri- ventricular sclerosis forms a broad zone so 

 extensive as to involve the whole of the floor, sides, and roof of the ventricle and the com- 

 plete vermis : from this zone projections of sclerotic tissue pass anteriorly into the middle 

 peduncle, cutting it across on one side and reaching to the surface of the pons, and laterally 

 and posteriorly into the white matter of the cerebellum. In the remaining portion of the 

 pons several dense and early irregular areas are found. Two He to one side of the median 

 raphe and are united by a narrow band : they involve the pyramidal fibres, the transverse 

 middle peduncle fibres, and the grey nuclei of the pons. Other three lie just in front of 

 the trapezium and involve very much the same fibres as the last. The zone of sclerosis 

 along the lateral sides of the ventricle extends into the hilum of the dentate nucleus on both 

 sides. Several other areas are found, affecting the lamellae of the dentate nuclei, and the 

 white matter of the cerebellum. On the right side the patches are oval, sharply defined 



