VI 



FORM AND FUNCTION 



1 1 



marrow will be a great advantage. This will W clear 

 if we take two cubes, a side of one of which is twice 

 the length of a side of the other. 



Then the face is four times as large and the cubic 

 contents eight times as large. This will be true of other 

 figures besides cubes, so that if the average girth of one 

 bone be double that of another, and if the length also be 

 double, its cubic contents will be approximately eight 



Fig. 2q. — Cubes. 



times as great ; and as the walls do not thicken in pro- 

 portion to the increased girth, nearly all the enlarged 

 interior can be filled with air. Clearly, then, a large 

 bird has much more to gain by dispensing with marrow 

 than a small one. 



Thus the Eagle has gained in point of lightness. It 

 must also have gained in point of strength, for in- 

 creased length of wing means an altogether dispro- 

 portionate increase of work. The longer the wing, 



I 



