4 THOMAS DWIGIIT OX THE 



sufficiently extended surface of origin, and again it is necessary for leverage that-many 

 muscles, at least, sliould be attached to projections. AVe find, therefore, that the whole 

 shape of a bone is determined so as to meet other than the static requirements. As for 

 processes like the ti'ochanters no one denies that tliey serve for muscular attachment. 

 I have elsewhere' liublished some notes on the structure of bone beneath processes for 

 the insertion of muscles and ligaments. In some cases, notably when the process is 

 very small, like the anterior inter-trochanteric ridge of the femur, the shaft is continued 

 beneath a layer of cancellated tissue. When the process is larger the surfiice of the 

 shaft seems to go round it i-ather than under it. The shaft is sometimes, but by no 

 means usually, found continued under the tubercle of the human radius and the coronoid 

 process of the ulna. It is sometimes re[)resented by jihites recalling the process which 

 Bigelow'- has named the "true neck of the femur" which, when very Avell developed, 

 appears to represent the posterior wall of the neck continued beneath the lesser tro- 

 chanter. As a rule, however, there is no well-marked separation of the cancellated 

 tissue of an}- of the larger processes from that of the main bone beneath. The third 

 trochanter of the horse (fig. 1) is a striking instance. One would be inclined to look 

 for a continuation of the shaft beneath it to support the weight, but such is not the case. 

 It being then admitted that the shape of bones shows provision both for a sufficient 

 extent of muscular origin and for tendinous insertions it remains to see what internal 

 arrangement of the laminae is found in the processes. Of course in cases Avhere what 

 would be the shape of the bone, were static needs the only ones, has been modified to 

 admit of a lai-ger space for muscular origin, it follows that the internal structure must 

 also of necessity be modified; Init an important and difficult question is whether tlie 

 internal structure shows any special arrangement to resist the pull of the muscles and 

 whether any of the bony plates are continuous with tendinous or ligamentous insertions. 

 I am strongly inclined from the study both of sections of dry bone, and of bones decal- 

 cified with the soft pai-ts unremoved, to reply to both questions in the negative. Lig- 

 aments and tendons are, I believe, never inserted at right angles to the surface of a bone. 

 They spread out over it, being inseparably united with the periosteum and in some cases 

 with cartilages. Thus the strain is dilfused over a larger surface. It is \evy remarkable 

 to what thin surfaces and to what weakly supported ones powerful muscles are attached; 

 familiar instances are the tuberosities of the humerus and the trochanters of the femur 

 in man. The cancelli inside of these processes are light and seem arranged to support 

 the delicate shell of bone and not to resist muscular action. In some few places, as for 

 instance at the back and underside of the os calcis, there are series of plates that seem 

 to represent fibres from the tendo Achillis and the plantar ligaments, but I have not been 

 able to satisfy myself of any continuity in decalcified specimens. Be that as it may, 

 such systems are exceptional. 



To sum up to this point it a[)pears that the shape of the bone depends not soleW on 

 its needs as an organ of sujjport but also on its needs as a fixed point for the origin and 

 insertion of muscles. Further, tliat although this modification in shape must necessarily 

 demand a change of the internal architecture, yet this change is only what is requisite 



'Remarks on the l^usition of Uie Fcimn- aiul on ils so- - Tlic Hip (I'liihulclphiu, llonry C. Leu) 1800; also The 

 ciiUed "Trne Neck." Journal ol' Anatomy and riiysiology, Boston Medical and Surgical Journal, 1875. 

 Vol. IX, 1875. 



