OSSIFICATION. 375 



hollow, are rendered considerably stronger than 

 if the same materials had been collected into a 

 solid cylinder of the same length. We may 

 farther remark, that as it is in the middle of 

 the shaft that the strain is greatest, so it is here 

 that the cavity is largest, and the resistance 

 most effectual. 



3. Formation and Developenietit of Bone. 







BUT it is not enough to contemplate the pur- 

 poses so admirably answered by these arrange- 

 ments. Our curiosity cannot but be powerfully 

 excited to learn what processes and refined se- 

 ries of means are employed by nature to raise 

 and to perfect all these artificially contrived 

 structures. It fortunately happens that in this 

 instance we are permitted to penetrate a little 

 farther than usual into the secrets of organic 

 evolution : for the succession of changes can be 

 better followed by the eye in the slow develope- 

 ment of the harder parts, than in the quicker 

 growth of mere yielding and expansible tex- 

 tures. The peculiar material also, of which bone 

 is formed, is easily distinguished by its hardness, 

 its whiteness, and its opacity from the softer and 

 more transparent animal substance with which 

 it is intermixed. Hence we are allowed an op- 



