950. Why are the motions of the heart, &c., made independent of the will?
Because, as the necessity for the heart's motion is fixed and unalterable, the constant motion of the heart could be best secured by giving it a fixed nervous influence, by which it might be unfailingly prompted to fulfil its functions.
If the movements of man's heart were subject to his will, he would be constantly required to regard the operations of that organ; and so large an amount of mental care and physical exertion would have to be employed in that direction, that man's sole work would be to keep himself alive. Hence we see the goodness of the Creator in giving life to man, and in keeping the vital impulses under his divine care.
CHAPTER XLVII.
The nerves are branches of the brain and the spinal cord; they are distributed in great numbers to all the active and sensitive parts of the body.
The spinal cord is a long and large cord of nervous matter, which extends from the brain through a continuous tube formed by corresponding hollows in the bones of the back. It serves as a nervous trunk for the distribution of nerves, just as the aorta distributes branches of blood-vessels.
953. Why is the spinal cord placed in the grooves formed by the back-bone?