180 JOHN C. KOCH 



If the external form and inner architecture of normal bone 

 represent the adaptation to normal function only, then altera- 

 tions in the static demands made upon the bones must be fol- 

 lowed by corresponding changes in both their internal and 

 external structure. Such a transformation of structure would 

 produce deformity if the changed static conditions were suffi- 

 ciently large to produce a marked change of contour of the nor- 

 mal bone, or to cause a displacement from the natural normal 

 position. Such changes of contour or displacement from the 

 normal must be regarded as a physiological adaptation of the 

 structure to pathological mechanical conditions and therefore 

 to 'pathological function.' 



The doctrine of the functional form of bone, with its coral- 

 lary of the functional pathogenesis of deformity has been ably 

 set forth by Julius Wolff. The foundation upon which this 

 doctrine rests is the correspondence between the inner structure 

 of the upper femur and the lines of stress in the Fairbairn crane, 

 assumed to be of similar shape and loaded in a manner similar 

 to that of the normal femur, the analysis of the crane having 

 been made by the Zurich mathematician, Culmann. The mathe- 

 matical foundation thus established by analogy alone, has been 

 justly criticised on mathematical grounds so that it must be 

 admitted that the proofs thus far brought forward to demon- 

 strate the soundness of the mathematical basis of this doctrine, 

 though suggestive, are not conclusive. 



Being struck with the novelty of the problem of establishing 

 these mathematical relations, and impressed with the great 

 importance of determining the facts by mechanical analysis of 

 the femur by quantitative as well as qualitative methods, in the 

 fall of 1913 I began the studies which have culminated in the 

 preparation of this paper. 



A cknowledgments 



The anatomical material and supplies required for the prose- 

 cution of the studies, the results of which are embodied in this 

 paper, together with the necessary laboratory facilities have been 



