THE HISTOLOGY OF DISSEMINATED SCLEEOSIS. 615 



The sequence of the changes in the blood-vessels seems to me to be the follow- 

 ing : at an early stage the blood-vessels in an involved area become dilated and 

 engorged with blood. It is not a question so much of one central vessel as of all 

 the branches of one small vessel, and even the finest capillaries, are recognised ; the 

 vessels are in no way altered, and have no nuclear increase either in the intima 

 or adventitia. During the stage of marked glia cell proliferation and commencing 

 fat granule cell formation, in very numerous areas it has been impossible to 

 recognise any structural alteration. The impression of a new formation of blood- 

 vessels, both at this stage and at a much later one, is probably due to the engorge- 

 ment making each fine vessel stand out distinctly, especially when stained with 

 picro-fuchsin. Nowhere at this stage is the relation of individual parts of the 

 tissues altered. In a few cases there have been noted a proliferation of the 

 capillary endothelium and the possible passage outwards of the proliferated 

 endothelial cells into the tissues. At the stage of abundant fat granule cell forma- 

 tion, when these cell elements are passing into the lymph spaces of the adventitia, 

 every vessel in the affected zone is mapped out by a ring or rings of such cells 

 (figs. 10, 13). The smallest capillaries show a single row of cells (fig. 433), often 

 with an outer limiting membrane, stained pink with fuchsin or blue with Mallory's 

 connective-tissue stain : the presence of this outer limiting membrane to such a 

 row of cells seems a strong argument in favour of the existence of a thin adventitia 

 in the capillaries. If such an area, with fat granule cells crowding the vessel 

 sheaths and tissue spaces (fig. 434), be looked at, with low power, and especially 

 in celloidin sections, where it is more difficult to analyse the constituent elements, 

 the impression is given of a softened area with cell-infiltrated walls. The possi- 

 bility that areas at such a stage of development have been taken as illustrating 

 cell-infiltrated areas may explain the great significance that has been ascribed to 

 the vessels and to the inflammatory character of the process. This is still more 

 evident at a slightly later stage, when there is a reaction to the presence of these 

 fat granule cells in the adventitial spaces and a proliferation of their cell elements. 

 The cell proliferation is of a secondary nature, and is evident in uncomplicated cases, 

 we think, only at this stage. It is evident that there is a marked increase in the 

 nuclear content of the vessel walls, an increase in which the endothelium of the 

 capillaries shares. As the resorption processes advance there is a gradual removal 

 of the fat granule cell element in the adventitial spaces, but the cell body of many 

 of these cells has gradually disappeared in situ, leaving a deeply-stained, crenated 

 nucleus (fig. 14), and during this stage we get a further nuclear element added to 

 the nuclear increase in the vessel wall. The adventitia has had its fibrils dis- 

 sociated and its lymph spaces filled by the fat granule cells ; as these disappear the 

 lymph spaces, which remain distended for a considerable time during the advancing 

 sclerosis, are to a certain extent now occupied by a cell infiltration of another kind- — 

 these are the small, round, lymphocyte-like cells common to all chronic processes. 



