ANATOMY 



the quill of the bird's feather, and many other 

 familiar objects too numerous to mention. The 

 contrivance was discovered in the building of 

 plants and animals millions of years ago, and by 

 comparison man discovered it but yesterday, and 

 applies his discovery in manufacturing his tubular 

 bridge, the tubular frame of his bicycle, and in 

 many other ways. 



About the middle of last century the anatomist 

 first recognised that the spongy bone or lattice- 

 work arrangement of bony substance, as seen in the 

 expanded extremities of the thigh-bone, was not 

 an unintelligible or haphazard arrangement. By 

 careful study of the disposition of the minute bars 

 of bony substance constituting the lattice-work, 

 and estimating the chief stresses to which these 

 parts of the bone are subject during life, it was 

 discovered that the arrangement was such as to 

 render the bone wonderfully efficient in resisting 

 the forces to which it is subject, with the most 

 economical use of the bony material imaginable. 



The chief stresses to which the expanded ends 

 of a bone such as the thigh-bone are subject are 

 compressing or pushing forces and tension or 

 pulling forces. If the lattice-work at the lower 

 end of the thigh-bone be examined, the mechanical 

 value of the arrangement of the bars of the lattice- 

 work can be readily appreciated. In the standing 

 position the weight of the body presses vertically 



213 



