THE greater portion of the first Report deals with the subject of human trypanosomiasis, particularly in the Congo district. The trypanosomata are flagellated protozoa, which have been found to be parasitic in many animals, sometimes causing no symptoms, as in the rat, but sometimes associated with serious effects, as in the tsetse-fly disease of the horse. During the last few years trypanosomata have been found to be parasitic in man in various districts of West and Central Africa. If the infected person shows irregular fever without other marked symptoms the condition has been termed trypanosomiasis; if in addition there is somnolence and stupor, and later wasting, convulsions, and fatal coma, the condition is the dreaded sleeping sickness which has destroyed tens of thousands of lives in Central Africa. Much of the matter in the volume under review deals with the relationship between these two diseases.