976 ON FORM AND MECHANICAL EFFICIENCY [ch. 



cellous tissue as a sort of spongy network or irregular honeycomb * ; 

 but at length its orderly construction began to be perceived, and 

 attempts were made to find a meaning or "purpose" in the arrange- 

 ment. Sir Charles Bell had a glimpse of the truth when he asserted f 

 that "this minute lattice- work, or the cancelli which constitute 

 the interior structure of bone, have still reference to the forces 

 acting on the bone"; but he did not succeed in shewing what these 

 forces are, nor how the arrangement of the cancelli is related to them. 

 Jeffries Wyman, of Boston, came much nearer to the truth in 

 a paper long neglected and forgotten {. He gives the gist of the 

 whole matter in two short paragraphs: "1. The cancelli of such 

 bones as assist in supporting the weight of the body are arranged 

 either in the direction of that weight, or in such a manner as to 

 support and brace those cancelli which are in that direction. In 

 a mechanical point of view they may be regarded in nearly all these 

 bones as a series of 'studs' and 'braces.' 2. The direction of these 

 fibres in some of the bones of the human skeleton is characteristic 

 and, it is believed, has a definite relation to the erect position which 

 is naturally assumed by man alone." A few years afterwards the 

 story was told again, and this time with convincing accuracy. It 

 was shewn by Hermann Meyer (and afterwards in greater detail by 

 Julius Wolff and others) that the trabeculae, as seen in a longitudinal 

 section of the femur, spread in beautiful curving lines from the head 

 to the hollow shaft of the bone ; and that these linear bundles are 

 crossed by others, with so nice a regularity of arrangement that 

 each intercrossing is as nearly as possible an orthogonal one: that 

 is to say, the one set of fibres or cancelli cross 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 (in the year 1866) to come into his colleague 

 Meyer's dissecting-room, where the anatomist was contemplating 



* Sir John Herschel described a bone as a "framework of the most curious 

 carpentry: in which occurs not a single straight line nor any known geometrical 

 curve, yet all evidently systematic, and constructed by rules which defy our 

 research" (On the Study of Natural Philosophy, 1830, p. 203). 



f In Animal Mechanics, or Proofs of Design in the Animal Frame, 1827. 



X Animal mechanics : on the cancellated structure of spme of the bones of the 

 human body, Boston Soc. of Nat. Hist. 1849. Reprinted, together with Sir C. Bell's 

 work, by^ Morrill Wyman, Cambridge, Mass., 1902. 



i 



