LAWS OF BONE ARCHITECTURE 227 



femur. The distal 2 inches of this axis are formed as the pro- 

 longation of the axis of the shaft in order to simplify the figure, 

 no inaccuracy being involved thereby. 



Analysis of the mechanical properties of the femur 



1. Analysis of serial transverse sections. Serial transverse sec- 

 tions were cut from the right femur in the following manner. 

 An approximate longitudinal axis was drawn on the anterior 

 surface of the femur so as to lie midway between the lateral and 

 medial outlines of the bone when viewed from the anterior. 

 The position of this axis was approximately that indicated by 

 the axis BCDE in figure 14. Then at intervals of I inch, meas- 

 ured along this axis, lines were drawn perpendicular to it to 

 mark the positions of the transverse sections. In the curved 

 poition of the upper femur the dividing lines weie drawn per- 

 pendicular to the curve at successive points. As these divid- 

 ing lines in the curved portion intersected near a common 

 point, F, (fig. 14) this was taken as a common intersection of all 

 these lines except the second line, marked 2 in figure 14. In 

 this figure only the alternate dividing lines of the cur\^ed por- 

 tion are shown, and are indicated by 2, 4, 6, etc. 



The seiial sections thus marked out were sawed in planes 

 peipendiculai to the plane of figure 14, and passing through the 

 division lines marked at the j-inch intervals. In the curved 

 portion of the upper femur the method adopted in sawing the 

 sections was as follows: The first saw-cut was made through 

 line 1 (fig. 14), then a thin section was cut parallel to the first 

 cut; the next cut was made through the line marked 2, thus 

 cutting a wedge-shaped piece. The next saw-cut was made 

 parallel to the cut through line 2, making a thin section of uni- 

 form thickness. This procedure was continued until the straight 

 part of the shaft was reached, after which the sections were cut 

 at intervals of |-inch until the expansion of the lower femur 

 was reached at section 64. From this section to the lower 

 end of the femur thin sections were cut as in the head and neck 

 of the femur, except that the thicker sections were of uniform 

 thickness. 



