PATHOLOGICAL ANATOMY 19
instances, quite independent of other changes, relatively slight infiltrations occur around the peripheral vessels, especially the veins. Besides this infiltration of the adventitia, a perivascular exudate is sometimes seen. The round cells penetrate the sur- rounding tissues and enclose the vessels like a wall.
In the supporting tissue itself, masses of round cells often col- lect. These cells are derived from the vessels. Thus, in Plate II, No. 1, the upper left hand portion of the picture (anterior horn) shows the exudate to consist principally of perivascular cell groups surrounding the minute blood vessels and capillaries, around whose branches they are massed like clusters of grapes on the stem of a vine. When an area of dense cellular infiltration is present (Plate II, No. 3), its extent can be demonstrated by serial sections, to be limited to the area of distribution of a blood vessel. In other cases, the infiltration, however, is diffused through the supporting tissue and is without any apparent relation to the vas- cular supply. In some areas, an unmistakable relation to the ganglion cells can be observed. Forssner and Sjoval demon- strated that many of the small masses of cells are only the remains of neurophages, which have completely devoured the ganglion cells.
The morbid changes we have been dealing with occur chiefly in the anterior horn. But in the posterior horn, analogous altera- tions are almost constantly present. In most of my cases such changes were especially marked in Clarke's column in the lower dorsal and upper lumbar regions. (Plate II, No. 4, right.) Oc- casionally I was able to prove that the infiltrations were connected with the vessels of the posterior system. But recently I have sometimes found Clarke's column scarcely affected. In Marburg's experience, Clarke's column was invariably less affected than the anterior horn. As a rule, the changes in the posterior are less marked than in the anterior horns. But this rule has exceptions. For instance, the morbid process may extend with the same sever- ity throughout the greater part of the gray matter; or it may, as in the lower dorsal region in the majority of my cases, affect mainly the boundary zone between the anterior and posterior horns and gradually diminish in intensity towards the front and the back of the cord. Rarely the posterior horn is affected to a greater degree than the anterior. Cellular infiltration may occur in the
