374 Mr Appleton, The Influence of Function 



The Influence of F miction on the Conformation of Bones. By 

 A. B. Appleton, M.A., Downing College. 



[Read 7 March 1921.] 



Inspection in a museum of a series of mammalian skeletons is 

 sufficient to indicate some sort of relationship between the osseous 

 details and the locomotor abihties of the animal, whether on 

 plains, in the trees, or in water. 



The femur is a bone which, in association with neighbouring 

 bones and muscles, repays detailed study. 



We find something in common between the femora of jumpers 

 belonging to quite different animal groups, even though all may 

 not jump in exactly the same way. The same is true of runners 

 (cursorials). It is true in spite of the fact that each mammalian 

 group of hving forms tends to exhibit its own characteristic 

 musculature, skeletal features and probably, too, characteristic 

 nervous mechanisms. And it is to be presumed in the first place 

 that tendencies exhibited by cursorials, say, belonging to various 

 groups, may be legitimately regarded as adaptations. How far 

 their pecuhar musculature is really of advantage to them will be 

 discussed in the sequel. 



A short summary will be here given of some muscular pecu- 

 liarities of speciahsed cursorials, jumpers and arboreal mammals, 

 and their relationship to pecuharities of the femur discussed. 



To what extent such peculiarities are determined by' "en- 

 vironmental" influences acting in the individual requires not only 

 a study of ontogeny, but experimental investigation of the effect 

 of modifying the conditions of growth. In fact, a study of human 

 variations demands from us an answer to the question : Are all of 

 these variations of hereditary origin, as Pearson and Lee assert*? 



The great plasticity of bone under mechanical influences sug- 

 gests these influences as possible modifying circumstances during 

 ontogeny. In what manner bone will react, is, however, at present 

 ill-understood; though it seems unhkely that IVIanouvrier's sup- 

 position can be true, viz. that under transmitted pressure during 

 youth, a femur will bend as a vital process or reaction. We only know 

 of bending as a twig is bent when the pressure is too great for a femur 

 softened by rickets or osteomalacia. 



Bone, however, does react to stressf. If too httle stress falls 

 upon an adult bone, it undergoes partial atrophy; it becomes im- 



M.L"?wr" and Lee 'Long Bones of the EngUsh Skeleton,' Drapers' Companu 

 Memoirs {Biometric Senes), X und :s.i, -p-p. 267 287 company 



t Murk Jansen, ' On Bone Formation," 1920. 



