The material upon which these observations are based has been forwarded to me from Uganda, with the exception of the brain of a rabbit kindly given to me by Dr. Plimmer. By the desire of the Committee on Tropical Diseases of this Society, Colonel Bruce has given instructions to his assistants, and they have forwarded to me from Entebbe, material from cases of Sleeping Sickness, 24 in all; also portions of the brains of eight monkeys experimentally infected, two oxen, and one donkey. The tissues

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... have been preserved in Formol-Muller's solution, or they have been sent already embedded in paraffin after having been hardened a short time in formalin. Sections were cut of either 5 or 10 /x in thickness; they were stained by Romanowsky, Leishman, Nissl polychrome, or Weigert-Gram methods, thus enabling observations to be made regarding:-(a) The existence of trypanosomes or Leishman bodies. (b) Changes in the ganglion cells and neuroglia cells. (c) Changes in the blood, the endothelial cells of the vessels, and the peri-vascular spaces, and soft membranes. (d) The existence of micro-organisms. (e) The existence of plasma cells, and other cells indicative of chronic inflammatory degenerative changes. It may be mentioned that in a number of instances sections of the lymphatic glands, some of which were removed during life and others mortem, were examined by the same methods. The principal pathological conditions observed were either drawn or photographed. In every case of Sleeping Sickness, in which there were symptoms during life, the characteristic change (which I described in two cases reported by Sir Patrick Manson) of a chronic meningo-encephalitis was found. In every chronic case I have found also plasma cells of Marscholko, which by some observers were considered to be pathognomonic of another chronic meningo encephalitis, general paralysis of the insane. b 2 on July 19, 2018 http://rspb.royalsocietypublishing.org/ Downloaded from