LAWS OF BONE ARCHITECTURE 273 



Summary — laws of hone structure 



In the preceding paragraphs of this section it has been shown 

 that in every part of the femur there is a remarkable adaptation 

 of the inner structure of the bone to the mechanical requirements 

 due to the load on the femur-head. The various parts of the 

 fenuu' taken together form a single mechanical structure wonder- 

 fully well-adai)ted for the efficient, economical transmission of 

 loads from the acetabulum to the tibia; a structure in which 

 every element contributes its modicum of strength in the man- 

 ner required by theoretical mechanics for maximum efficiency. 



It has been indicated that, in each of the arbitrary divisions 

 into which the femur was divided for clearness of discussion, 

 the internal structure is everywhere so formed as to provide in 

 an efficient manner for all the internal stresses which occur due 

 to the load on the femur-head. Throughout the femur, with 

 the load on the femur-head, the bony material is arranged in 

 the paths of the maximum internal stresses, which are thereby 

 resisted with the greatest efficiency, and hence with the maxi- 

 mum economy of material. The conclusion is inevitable that 

 the inner structure and outer form of the femur are governed 

 by the conditions of maximum stress to which the bone is sub- 

 jected normally by the preponderant load on the femur-head; 

 that is, by the body weight transmitted to the femur-head 

 through the acetabulum. In the normal individual the maxi- 

 mum load on the femur-head occurs in running. 



In this paper it has been shown that the femur obeys the 

 mechanical laws that govern other elastic bodies under stress; 

 the relation between the computed internal stresses due to the 

 load on the femur-head, and the internal structure of the dif- 

 ferent portions of the femur is in very close agreement with the 

 theoretical relations that should exist between stress and struc- 

 ture for maximum economy and efficiency: and therefore, it is 

 believed that the following laws of bone structure have been 

 demonstrated for the femur: 



1. The inner structure and external form of human bone are 

 closely adapted to the mechanical conditions existing at every 

 point in the bone. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 21, NO. 2 



