LAWS OF BONE ARCHITECTURE 245 



In the calculations for these coefficients their values were 

 computed in each section at intervals of ts inch from the neutral 

 plane. 



In figure 18a is shown to scale the diagram of the intensity 

 of the horizontal and vertical shearing unit-stresses for section 

 8. It will be seen that the horizontal and vertical shearing 

 stresses are equal but are at right angles to each other as has 

 been explained in Part II, {50-51). 



6. Maximum unit-stresses in the femur. The axial unit- 

 stress in the femur is throughout a compressive stress. Hence 

 it combines with the compressive stress due to the bending 

 moment on the medial side of the femur, to produce maximum 

 compressive unit-stresses in the fibers most distant from the 

 neutral axis. 



The axial (compressive) unit-stress on the tensile side of the 

 femur balances or offsets an equal amount of tensile unit-stress 

 due to bending moment, thus decreasing the amount of the 

 tensile unit-stress. The true maximum tensile unit-stress is 

 therefore the difference between the intensity of the maximum 

 tensile unit-stress due to the bending moment and the intensity 

 of the axial compressive unit-stress. In figure 18a the axial 

 and bending moment stresses are shown to scale for section 8, 

 and the effect of the axial stress is seen in increasing the unit- 

 stress at every point on the medial side and decreasing the 

 tensile unit-stress at every point on the lateral side. 



The amounts of these maximum unit-stresses at various points 

 along the femur are shown numerically in table 6, diagrammati- 

 cally in figure 17 and the amounts and positions graphically in 

 figure 18. 



In figure 17 is shown a series of curves representing the maxi- 

 mum unit-stresses at every section due to the assumed load of 

 100 pounds on the femur-head. Curve 1 gives the intensity of 

 the unit-stress due to the axial load. Curve 3 gives the amount 

 of the maximum tensile unit-stress due to the bending moment 

 at the various sections, and curve 4 gives the amount of the 

 corresponding maximum compressive unit-stresses due to the 

 bending moment. Curve 2 gives the maximum amount of the 



