682 ON FOKM AND MECHANICAL EFFICIENCY [ch. 



lines from the head to the tubular shaft of the bone, and these 

 bundles of Hues were crossed by others, with so nice a regu- 

 larity of arrangement that each intercrossing was as nearly as 

 possible an orthogonal one: that is to say, the one set of fibres 

 crossed the other everywhere at right angles. A great engineer. 

 Professor Culmann of Zurich (to whom, by the way, we owe the 

 whole modern method of "graphic statics"), happened to see 

 some of Meyer's drawings and preparations, and he recognised 

 in a moment that in the arrangement of the trabeculae we had 



Fig. 335. Crane-head and femur. (After Culmann and H. Meyer.) 



nothing more nor less than a diagram of the lines of stress, or 

 directions of compression and tension, in the loaded structure : 

 in short, that nature was strengthening the bone in precisely the 

 manner and direction ih which strength was needed. In the 

 accompanying diagram of a crane-head, by Culmann, we recognise 

 a slight modification (caused entirely by the curved shape of the 

 structure) of the still simpler lines of tension and compression 

 which we have already seen in our end-supported beam as 

 represented in Fig. 332. In the shaft of the crane, the concave 



