Classicly

In a general way, we may compare the human body to three closed boxes, one above another. These boxes are the skull, the chest, and the abdomen. Each one has its own special contents, formed to do a special work for the body. The skull is a hard, bony case made to contain the brain. This is where the mind lives, and it is part of the work of the mind to take care of the body and direct its movements. The brain maintains a sort of telegraph station within 9itself.

Wires, which we call nerves, branch out from it to all parts of the body, and the brain is constantly receiving messages over these wires and sending others telling the muscles what to do. For instance, if the hand comes in contact with something hot, a message instantly goes to the brain, telling this fact. The brain sends back word to take the hand away, and the hand is withdrawn. But all this is done so quickly that the hand seems to be withdrawn the very instant that it comes in contact with the fire. The skull is supported by the backbone, which connects it with the second closed box.