NATURAL THEOLOGY. 



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ture of the heart, might say beforehand that it 

 would play: but he would expect, I think, from 

 the complexity of its mechanism, and the delicacy 

 of many of its parts, that it should always be 

 liable to derangement, or that it would soon work 

 itself out. Yet shall this wonderful machine go, 

 night and day, for eighty years together, at the 

 rate of a hundred thousand strokes every twenty 

 four hours, having, at every stroke, a great resist- 

 ance to overcome ; and shall continue this action 

 for this length of time, without disorder and with- 

 out weariness ! 



[This figure will assist the explanation of the following pages. 

 It presents a section of the ventricle and the artery. Suppose that 

 the blood enters in the direction of the arrow, it passes between 

 two valves of very particular construction. They are of a trian- 

 gular shape, and held out by little cords, which are called the 

 cord<B ttndinea. These cords are attached to muscles, which, 

 from their appearance, are called columnar carnece; and these 



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