Fig. 2. Frequency diagram of the values of the ratio K of the internal to external diameter of all investigated human femora from posterior (left diagram) and medial (right diagram) views. The Gaussian curves are fitted to the measured K-values. A vertical arrow shows the mean K_mean. Vertical lines represent the four theoretical optima K_Y, K_S, K_F, K_I given in Table 1. There are fewer K-values for medial than for posterior view, because we could not evaluate the medial radiograph of a few subadult and old-people femora with osteoporosis (in the contrast-poor radiographs the bone walls could be recognized neither computationally, nor visually).