LAWS OF BONE ARCHITECTURE 289 



bone and coni]);u*t bone are homogeneous materials and differ 

 chiefly in sti'ength apj^i-oximately in proportion to their densities. 

 2. The thickness and closeness of spacing of trabeculae in 

 bone vary directly with the intensity of the stresses transmitted 

 by them. 



Applications 



If the mechanical structure of bone is correctly understood , 

 the repair of fractiu'es and the general treatment of bone diseases 

 and deformities may be handled with greater efficiency and the 

 proper prophylactic measures against deformity may be under- 

 taken with greater hope of success. 



The theory of the functional form of bone proposed by Wolff 

 and also by Roux ('81) with that of the functional pathogenesis 

 of deformity, though long supported by abundant clinical evi- 

 dence and practically applied by many surgeons and orthope- 

 dists as a working basis in the treatment of deformities, has been 

 the subject of so much controversy that much confusion has 

 arisen as to the value of the theory in every-day practice. 



The mathematical demonstration of the relation between the 

 form and the function of bone under normal conditions as pre- 

 sented in this paper is believed to place this theory upon a sound 

 foundation. The close adaptation of the structure of normal 

 bone to its function leads logically to the conclusion that con- 

 tinued deviation from the normal static conditions to which a 

 bone is subjected must be followed by a structural adaptation 

 to meet the changed conditions (altered function). 



Whether the persistent altered static (mechanical) conditions 

 in the bone be due to fracture, bone disease, paralysis followed 

 by postural changes, or other causes, the fundamental mechani- 

 cal principles apply with equal force: transformation of the 

 inner structure of bone takes place, and the inner structure of 

 the bone is altered with mathematical accuracy to conform to 

 the new mechanical conditions usuall}^ with a high degree of 

 economy. 



Fractures unite without deformity when there is good co- 

 aptation because in such a case the original mechanical condi- 



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



