NATURAL THEOLOGY. 31 



happened to be more crowded, or more feeble than 

 common, bending the head down in the act of tying 

 a shoe or drawing on a boot. Children and tumblers, 

 being much in the habit of placing their bodies in all 

 positions, feel no inconvenience from having the head 

 downwards, because blood vessels always become 

 strong enough to bear the pressure to which they are 

 habitually exposed ; but to many old people ac- 

 customed to keep the head always upright, the 

 attempt to imitate such feats would be dangerous. 

 This will lead you to appreciate the remarkable pro- 

 vision to which I alluded. Can you describe it ? 



A. The principal blood vessels which carry up 

 the blood into the brain, and about one tenth part of 

 the whole blood in the body, it is said, is thrown into 

 that organ, are so contrived, that the force -of the 

 stream, and it is thrown with a smart stroke, owing to 

 the nearness of the heart, is principally spent against 

 the bone of the skull. The provision is this. The 

 main artery of the head makes a sudden turn in the 

 base of the skull, by which the force of the current 

 is broken, and then distributes itself over the brain ; 

 the consequence of which is, the discharge is made 

 against the bony walls of the skull. It is like a 

 stream of water from an engine, striking against the 

 side of a building, which being done, the water drips 

 down or diffuses itself without any considerable vio- 

 lence. In quadrupeds, the position of whose heads t 

 being nearly upon the same line with their heart, 

 exposes the blood to flow with more force into the 

 brain, the blood vessels, where they enter the skull, 



