are greatly attenuated through wasting of their muscular coat, while at the same time the mucous lining is hyperæmic and, not infrequently, ulcerated. The liver and spleen are usually atrophied. The suprarenal capsules may be larger than normal, and the cortex may be black, while the medulla is whitish in colour, but as a rule they are perfectly normal.
There may be actual wasting of the brain, and the ventricles may be distended by an excess of fluid. In the cord the lateral columns and the crossed pyramidal tract are especially implicated, but the direct cerebellar tracts usually escape. The anterior cornual cells are frequently atrophied and deeply pigmented. The posterior columns do not escape, the median portion being often degenerated. The degenerative changes in the lateral columns are chiefly in the middle and lower third of the dorsal region, those of the posterior columns principally in the cervical and upper dorsal region.
Mott (Brit. Med. Journ., July 3rd, 1913) has given a detailed account of the histological changes in the nervous systems of two cases of pellagra one of English, the other of Egyptian origin. He remarks as to the changes in the cerebrum, cerebellum, pons, medulla, and spinal cord, that in none of the sections was there any evidence of meningeal or peri vascular infiltration with lymphocytes, plasma cells, or polymorphonuclear leucocytes. This absence of chronic meningo-encephalitis, a chronic inflammatory condition so characteristic of certain protozoal diseases, contraindicates the protozoal theory of pellagra, although it cannot be said to disprove it, for in malaria the vessels may be crowded with parasites and yet no perivascular or meningeal reaction be detectable. Moreover, although all the changes were like those produced by a chronic toxæmia, the cause of that toxæmia has not been demonstrated. All the posterior spinal ganglia cells showed, in varying degree, a marked chromatolysis, swelling of cells, and disappearance of Nissl's granules, and all the anterior horn cells and their hornologues in the medulla and pons a varying degree of peri-
