116 



NATURAL THEOLOGY. 



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[Three views of the knee-joints.] 



direction, and by advancing it further out from 

 the centre of motion ; and this upon the principles 

 of the resohition of force, upon which principles 

 all machinery is founded. These are its uses. 

 But what is most observable in it is, that it ap- 

 pears to be supplemental, as it were, to the frame : 

 added, as it should almost seem, afterward ; not 

 quite necessary, but very convenient. It is se- 

 parate from the other bones : that is, it is not con- 

 nected with any other bones by the common 

 mode of union. It is soft, or hardly formed, in 

 infancy; and produced by an ossification, of the 

 inception, or progress of which no account can be 

 given from the structure or exercise of the part. 



VI. The shoulder-blade is, in some material re- 

 spects, a very singular bone : appearing to be made 

 so expressly for its own purpose, and so indepen- 

 dently of every other reason. In such quadrupeds 

 as have no collar-bones, which are by far the greater 

 number, the shoulder-blade has no bony commu- 



