Abstract: A teaching aid for use in explaining the biochemical and/or physiological basis of human body function in health or when suffering from a pathological condition such as diabetes mellitus. The teaching aid comprises means representing the blood stream, organs and cells and a plurality of sets of tokens representing chemical or biochemical substances. The blood stream is represented as substantially linear. The organs and cells are represented as substantially the same size and are positioned in direct communication with the blood stream representing means. The tokens are moved along the blood streams representing means and into and out of the organ and cell representing means to demonstrate the functions of the organs and cells.