UC NATURAL THEOLOGY. 



been sufficient. The translation of the blood in the heart 

 itself is after this manner. The receiving cavities respec- 

 tively communicate with the forcing cavities, and, by their 

 contraction, unload the received blood into them. The 

 forcing cavities, Avhen it is their turn to contract, compel the 

 same blood into the mouths of the arteries. 



The account here given will not convey to a reader igno- 

 rant of anatomy any thing like an accurate notion of the 

 form, action, or use of the parts — nor can any short and pop- 

 ular account do this — but it is abundantly sufficient to testify 

 contrivance ; and although imperfect, being true as far as it 

 goes, may be relied upon for the only purpose for which we 

 offer it — the purpose of this conclusion. 



" The wisdom of the Creator," says Hamburgher, " is 

 in nothing seen more gloriously than in the heart." And 

 how well does it execute its office. An anatomist, who 

 understood the structure 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 resistance to overcome ; and 

 shall continue this action for this length of time without dis- 

 order and without wearmess I 



But further, from the account which has been given ol 

 the mechanism nf the heart, it is evident that it must require 

 the interposition oi^ valves — that the success indeed of its ac- 

 tion must depend upon these ; for when any one of its cavi- 

 ties contracts, the necessary tendency of the force will be to 

 dri\'e the enclosed blood not only into the mouth of the ar 

 ter^' where it ought to go, but also back again into the mouth 

 of the vein from which it flowed. In like manner, when by 

 the relaxation of the fibres the same cavity is dilated, the 

 blood would not only Fin into it from the vein, which was 



