176 NATURAL THEOLOGY. 



will not say upon our effort, but upon our bidding, 

 our care, or our attention, they would leave us 

 leisure for nothing else. We must have been 

 continually upon the watch, and continually in 

 fear ; nor would this constitution have allowed of 

 sleep. 



It might perhaps be expected, that an organ 

 so precious, of such central and primary import- 

 ance as the heart is, should be defended by a 

 case. The fact is, that a membranous purse or 

 bag, made of strong, tough materials, is provided 

 for it : holding the heart within its cavity : sitting 

 loosely and easily about it; guarding its sub- 

 stance, without confining its motion ; and contain- 

 ing likewise a spoonful or two of water, just 

 sufficient to keep the surface of the heart in a 

 state of suppleness and moisture. How should 

 such a loose covering be generated by the action 

 of the heart ? Does not the enclosing of it in a 

 sack, answering no other purpose but that enclo- 

 sure, show the care that has been taken of its pre- 

 servation ? 



One use of the circulation of the blood probably 

 (amongst other uses) is, to distribute nourishment 

 to the different parts of the body. How minute 

 and multiplied the ramifications of the blood-ves- 

 sels for that purpose are ; and how thickly spread 

 over at least the superficies of the body, is proved 

 by the single observation, that we cannot prick 

 the point of a pin into the flesh without drawing 

 blood, i. e. without finding a blood-vessel. Nor 



