236 JOHN C. KOCH 



parallel to the line of action of the load, W, which acts in the 

 direction AB. 



Hence, at successive points along the axis of the femur the 

 load, W, is resolved into two components parallel and perpen- 

 dicular, respectively, to the axis EDCB. The component 

 parallel to the axis at any given point is the axial load, and the 

 component at right angles to this force is the vertical shear at 

 the given point. Vertical shear is therefore the component of 

 the load which is perpendicular to the axis of the bone. 



In figure 14 the lines marking the successive sections are in- 

 dicated by the radial lines 1, 2, 4, 6, etc., all of which except 

 1 and 2, intersect at a common point F. These lines have 

 been discussed in greater detail in a preceding section, under 

 the heading, ''Analysis of serial transverse sections" (p. 227). 



2. Resolution of load. A. Axial load and vertical shear. 

 In order to determine graphically the amount of the axial and 

 of the vertical shearing force at successive sections of the femur 

 under the assumed load, pass a line FJ in figure 14, through F 

 and parallel to AB. The force W, is laid ofT to scale as FJ, 

 and for simplicity it will be assumed to be 100 pounds. By this 

 means percentages of the load may be readily computed, and 

 subsequently the stresses finally determined, may be calculated 

 for any other load on the femur by simple proportion. The 

 accuracy of the calculations is not affected by this procedure 

 and the labor of computation is much reduced. 



From the point J draw the lines JK, JL, JM, JN., JO, JP, 

 JQ, and JR, perpendicular respectively to the radial lines F4-, 

 F6, F8, FIO, F12, FI4, F16 and F17. Then the line JK repre- 

 sents to scale the direction and amount of the component of W 

 which acts at right angles to FJf., or the axial load acting on sec- 

 tion 4 of the femur. Likewise, FK represents the component of 

 W which acts in a direction perpendicular to the axis of the 

 femur at section 4, and therefore represents the vertical shearing 

 force at that section. 



In the same manner the components of W which form the 

 axial force and the vertical shearing force at successive sections 

 are indicated in figure 14. The axial forces are indicated at 



