XVI] THE STRUCTURE OF BONE 683 



or inner side, overhung by the loaded head, is the " compression- 

 member"; the outer side is the "tension-member"; and the 

 pressure-lines, starting from the loaded surface, gather themselves 

 together, always in the direction of the resultant pressure, till 

 they form a close bundle running down the compressed side 

 of the shaft : while the tension-lines, running upwards ^long the 

 opposite side of the shaft, spread out through the head, ortho- 

 gonally to, and linking together, the system of compression-lines. 

 The head of the femur (Fig. 335) is a little more comphcated in 

 form and a httle less symmetrical than Culmann's diagrammatic 

 crane, from which it chiefly differs in the fact that the load is 

 divided into two parts, that namely which is borne by the head 

 of the bone, and that smaller portion which rests upon the great 

 trochanter ; but this merely amounts to saying that a notch has 

 been cut out of the curved upper surface of the structure, and we 

 have no difficulty in seeing that the anatomical arrangement of 

 the trabeculae follows precisely the mechanical distribution of 

 compressive and tensile stress or, in other words, accords perfectly 

 with the theoretical stress-diagram of the crane. The lines of 

 stress are bundled close together along the sides of the shaft, and 

 lost or concealed there in the substance of the sohd wall of bone ; 

 but in and near the head of the bone, a peripheral shell of bone 

 does not suffice to contain them, and they spread out through the 

 central mass in the actual concrete form of bony trabeculae*. 



* Among other works on the mechanical construction of bone see : Bourgery, 

 Traite de Vanatomie (I. Osteologie), 1832 (with admirable illustrations of trabecular 

 structure); Tick, L., Die Ursachen der Knochenformen, Gottingen, 1857; Meyer, H., 

 Die Architektur der Spongiosa, Archiv f. Anat. und Physiol. XLvn, pp. 615-628, 

 1867 ; Statilc ii. Mechanik des menschlichen Knochengeriistes, Leipzig, 1873 ; 

 Wolff, J., Die innere Architektm- der Knochen, Arch. f. Anat. und Phys. L, 1870; 

 Das Oesetz der Transformation bei Knochen, 1892; von Ebner, V., Der feinere Bau 

 der Knochensubstanz, Wiener Bericht, Lxxii, 1875; Rauber, Anton, Elastizitdt und 

 Festigkeit der Knochen, Leipzig, 1876; 0. Meserer, Elast. u. Festigk. d. mensch- 

 lichen Knochen, Stuttgart, 1880; MacAlister, Sir Donald, How a Bone is Built, 

 English Illustr. Mag. pp. 640-649, 1884; Rasumowsky, Architektonik des Fuss- 

 skelets. Int. Monatsschr. f. Anat. p. 197, 1889; Zschokke, Weitere Unters. liber das 

 Verhdltniss der Knochenbildung zur Statik und Mechanik des Vertebrate nskelets, 

 Ziirich, 1892; Roux, W., Ges. Abhandlungen iiber Entwicklungsmechanik der 

 Organismen, Bd. I, Fuyiktionelle Anpassung, Leipzig, 1895; Triepel, H., Die 

 Stossfestigkeit der Knochen, Arch. f. Anat. u. Phys. 1900; Gebhardt, FunktioneU 

 wichtige Anordnungsweisen der feineren und groberen Bauelemente des Wirbel- 

 thierknochens, etc.. Arch. f. Entw. Mech. 1900-1910; Kirchner. A., Architektur 



