SIGNIFICANCE OF BONE STRUCTURE. 3 



sequently have a system in the main longitudinal. Finally, there are the shafts of the 

 long bones, the solid walls of which break up into plates near their ends. Moreover 

 there are plates near the ends of bones which he thinks must be considered continuations 

 of tendons. 



Eoux^ of Breslau, in a paper in which ho analyzes the internal structure of an anchy- 

 losed knee, makes a further classification which, though very good, is rather long to be 

 given here especially as it is more minute than the purposes of this paper require.^ 



That tlie internal structure of bone shows a well-planned architecture suited to the 

 mechanical requirements of the part is an axiom so generally accepted that we may take 

 it as a starling-point, although, as will appear later, it requires considerable modification. 

 There are, indeed, many aspects to the question, Avhlch is one of no common difficulty. 

 Although some of the most thorough of the authors mentioned above have referred to 

 the mechanical requirements in the widest sense, it seems that many, if not most, writers 

 have looked upon bones mei'ely as weight-bearing appliances. Considered in this light 

 alone the question is not a simple one. Is the ariangement of the plates that requisite 

 when the bone is in the position of the greatest strain? If not, it is clear that there 

 must be what builders call a large factor of safety, that is, that much more material 

 must be disposed along the stress lines than would otherwise be necessary. Another 

 point not to be lost sight of is that, besides the actual weight a bone may have to bear, 

 it must be able to resist compression against the next bone to which it is subjected by 

 muscular action. 



But if we look on bones as not merely adapted to weight-bearing but as serving also 

 for the origin and insei-tion of muscles, do we find the plan of the bone modified for 

 these requirements? There seems no possibility of doubting it. The femur of a quad- 

 ruped inclines downward and forward. If Ave suppose the upper part to be made of 

 the least amount of bone sufficient to bear the weight, it is clear that the shaft at the 

 neck would be thicker from before backward than transversely, as the strain conies 

 in the former direction. But the contrary occurs: the greatest breadth is transverse. 

 Clearly then there are other factoi-s than the purely static needs of the bone. If this 

 shape be for the purpose of resisting any strain it must be that of the muscles. Although, 

 as I shall undertake to show later, certain structures occur that are in no way teleolog- 

 ical, it is hard to believe that so important a feature as this widening of the femur should 

 be purposeless, and we are almost forced to hold that either it is to give greater surface 

 for muscular origin and insertion, or that it is to resist lateral tension from muscular 

 action, or that the two reasons coexist. 



The precise part played by muscles is extremely difficult to determine. "With them 

 it is proper to associate ligaments, there being no doubt that what is a ligament in some 

 animals is a muscle in others and, moreover, it seems a matter of no consequence whether 

 the strain is applied to a bone by the pull of a muscle on a tendon or less directly by 

 making tense a ligament. There seems no doubt that a fiictor in the shape of bones, 

 besides weight-bearing, is muscular attachment. Clearly a large muscle must have a 



'Beitiiige zur Morpliologie der fmiclioiicllen Aiipassung. ten on Uie growth of bone nor on the arrangement of the 

 Arohiv fiir Anat. und Entwick., 1885. cancclli in pathological conditions. 



-It is not thonglit necessary to discuss what has been writ- 



