rapid and accurate measurement of growth of solid tumours and changes in the tumour bed in the rat by the technique of volumetric displacement an apparatus which has been widely used in rats for measuring swelling of the foot induced locally by inflammatory agents has been adapted to measure rapidly accurately and objectively the growth of tumour cells transplanted to the foot and the reactions of the normal tissues tumour bed to tumour growth general features on the apparatus and the techniques used are described examples are provided of preliminary measurements made of normal growth of the foot reactions of the foot to two injurious agents histamine and corynebacterium parvum and of growth of allogeneic w256 tumour cells