XVI] THE STRUCTURE OF BONE 977 



the section of a bone*. The engineer, who had been busy designing 

 a new and powerful crane, saw in a moment that the arrangement 

 of the bony trabeculae was nothing more nor less than a diagram 

 of the lines of stress, or directions of tension and compression, in 

 the loaded structure: in short, that Nature was strengthening the 

 bone in precisely the manner and directioi^ in which strength was 

 required; and he is said to have cried out, "That's my crane!" 



Fig. 462. Head of the human femur in section. After Schafer, from 

 a photo by Professor A. Robinson. 



In the accompanying diagram of Culmann's crane-head, we recognise 

 a simple modification, due entirely to the curved shape of the 

 structure, of the still simpler Hues of tension and compression which 

 we have already seen in our end-supported beam, as represented 

 in Fig. 460. In the shaft of the crane the concave or inner side, 



* The first metatarsal, rather than the femur, is said to have been the bone 

 which Meyer was demonstrating when Culmann first recognised the orthogonal 

 intercrossing of the cancelli in tension and compression; cf. A. Kirchner, Architektur 

 der Metatarsalien des Menschen, Arch. f. Entw. Mech. xxiv, pp. 539-^16, 1907. 



