It has become increasingly evident from our studies on the rat that the beam strength of the fibula varies in general with the body weight. When, for example, we plotted the strength of the fibulas of normal rats selected at random as a function of their body weight, the strength of the bones increased as the weight increased.1 Again, when we started rats of approximately the same age on a diet on which it happened that they lost weight because they progressively ate less, their fibulas lost strength iikewise.2 It seems, therefore, that there is a definite strength of bone per unit of body weight, and that the strength of the weightbearing bones varies directly with function (Wolff's law).
In spite of this general relationship between the strength of bone and the body weight, however, the ratio of the one to the other can be altered experimentally. The