Considering the placenta from the functional point of view as an exchange organ be- tween mother and foetus, it is noteworthy that placentas of all types have a common structural principle in that all placentas have structures enlarging the surface area avail- able for exchange, as is also the case with other organs with similar functions, such as the lungs, kidneys and intestine. It may therefore be assumed that a quantitative rela- tionship must exist between the structure of the placenta and its function. Accurate information on this relationship could contribute to better understanding of...