XVI] ON THE SKELETON AS A WHOLE 1017 



triumphs of modern mechanism as a torpedo, a racing aeroplane, 

 a high-speed rail way- train, the whole construction is knit together 

 in a new way. It finds its streamlined outline in what seems to 

 be a simple and natural way; it is solid and robust, it is graceful 

 as well as strong; it is no longer a bundle of parts, it has become 

 an organic whole : its likeness, even its outward likeness, to a living 

 organism has becorne patent and clear. 



Throughout this short discussion of the principles of construction, 

 we see the same general principles at work in the skeleton as a whole 

 as we recognised in the plan and construction of an individual 

 bone. That is to say, we see a tendency for material to be laid 

 down just in the lines of stress, and so to evade thereby the 

 distortions and disruptions due to shear. In these phenomena 

 there lies a definite law of growth, whatever its ultimate expression 

 or explanation may come to be. Let us not press either argument 

 or hypothesis too far: but be content to see that skeletal form, as 

 brought about by growth, is to a very large extent determined by 

 mechanical considerations, and tends to manifest itself as a diagram, 

 or reflected image, of mechanical stress. If we fail, owing to the 

 immense complexity of the case, to unravel all the mathematical 

 principles involved in the construction of the skeleton, we yet gain 

 something, and not a little, by applying this method to the famihar 

 objects of anatomical study: ohvia conspicimus, nubem pellente 

 tnathesi*. 



Before we leave this subject of mechanical adaptation, let us 

 dwell once more for a moment upon the considerations which arise 

 from our conception of a field of force, or field of stress, in which 

 tension and compression (for instance) are inevitably combined, and 

 are met by the materials naturally fitted to resist them. It has 

 been remarked over and over again how harmoniously the whole 

 organism hangs together, and how throughout its fabric one part 

 is related and fitted to another in strictly functional correlation. 

 But this conception, though never denied, is sometimes apt to be 

 forgotten in the course of that process of more and more minute 



* The motto was Macquorn Rankine's, \vl 1857; cf. Trans. R.S.K. xxvi, p. 715, 

 1872. 



