independent of each other as if they belonged to different

bodies and lived in different worlds.

Nevertheless, as we all this beating of the heart. stops and fails to start again we shall die, but from year's end to year's end we think nothing about it. At night we lie down to sleep with no anxiety lest the steady pulsing should cease. By day we run, dance, dive, swim ; we play leapfrog and football; we walk on our hands and turn somersaults, knowing all the while that the heart is affected by every move we make; but, through all that we do, we seem also to know that somehow the body has an arrangement for controlling its most important life machinery whether we pay attention to it or not.

know, life itself depends on We know that whenever it

And so it has. Up and down on each side of the backbone is a chain of ganglia which holds more vital power, perhaps, than any other part of the nervous system. It seems to be nature's device for relieving the brain-a device for keeping the vital machinery in running order whether the owner of the machinery gives heed or ignores it.

There we have it then! We have come upon the mystery of the so-called sympathetic nervous system; the mystery of the neurons and ganglia which take charge of internal, bodily affairs-neurons which do their faithful work whatever our commands to them may be. This work is in charge of what is called the

sympathetic nervous system. So far as location and arrangement are concerned, it is not very difficult to understand the facts about this system, and the following outline will give them as simply as possible.

1. Forty-nine ganglia unite to form the main part of the sympathetic nervous system. These ganglia belong together as a complete set. Twenty-four lie on one side of the backbone, twenty-four on the other side, and one lies in front of the very last bone of the back.

2. Each of the forty-nine ganglia is connected with its neighbor above and its neighbor below by what might be called a rope of axons.

3. This string of ganglia, held together by an axon rope, seems to hang like a loop, with the backbone as a pole in its center.

SPINAL CORD WITH
SPINAL NERVES

4. The neurons of the differ- On the left are a few sym

ent ganglia send axons off to

definite parts of the body-to

pathetic ganglia joined

by their rope of

axons

heart, stomach, liver, and elsewhere. At these different places the axons are so closely woven together that they form a network called a plexus; small ganglia are interlaced with each plexus.

5. One very important plexus is near the heart, another near the stomach.

On the street the other day my four-year-old friend suddenly bent his head forward and thumped it into the stomach of an elderly man who came that way. The boy was surprised when the old man bent himself double and almost groaned aloud, for the child himself knew nothing about the plexus of axons near the stomach, neither did he know that wherever axons are thickest there it hurts most to be punched. The boy's brother, fourteen years old, understood the situation perfectly. He thought the man really needed to groan, "because," as he said, “you see it hurts awfully to be thumped in your stomach like that."

Each ganglion receives some axons from the spinal cord; and this shows that even though we cannot control the neurons of the sympathetic ganglia by our will power, they are, nevertheless, working hand in hand with the neurons of the brain.

CHAPTER XIX

THE WAY TO GOVERN THE GANGLIA

If you really wish a faster heart beat, spend two or three minutes in taking swift, vigorous exercise of one sort or another. Either chase a car down street, race upstairs, or go through some set of energetic gymnastic exercises; then count your pulse. You will find that you have sent it bounding upward from seventy to one hundred and twenty or more throbs a minute.

This test will prove that although you cannot increase your pulse beat by giving direct commands, you can still get the result in an indirect way. Your thinking neurons can set muscles to work; these muscles call for blood; this call compels the ganglia which control the heart and blood vessels to issue prompt orders for rapid work. They force the heart to go to work with a will, expanding and contracting, contracting and expanding, with every throb you feel.

Other parts of the body are constantly influenced in the same way; that is, certain sets of neurons seem to hold the whip hand over certain other sets, compelling them to do what otherwise they would not have done.

This fact explains the unconscious service which we often get in various other directions.

When I think of ice cream and candy, of peaches and strawberries, for example, the neurons of the salivary glands are so affected that they set the glands to work and my "mouth waters." When I am hungry and think of eating, the neurons of the stomach compel gastric juice to flow. The work of digestion is in this way helped by the mere fact of being hungry. Thus, in one direction and another, entirely without our knowledge, different groups of neurons toil for our welfare.

Every day, by still other methods, and without our planning for it, the mind governs the ganglia like a lordly tyrant.

Such was the case with a woman who suffered because her baby suffered. Dr. Carpenter writes about it. This woman was watching the child at play; saw the tiny hand on the sill of the open window; saw the heavy sash fall with a crash and cut off three baby fingers; and at once, while the child screamed, she herself suffered great pain in her own hand. The doctor did what he could for the baby, then turned to the mother, who was now moaning and groaning with pain. He found that three of her fingers were red and swollen; and, strange to say, these very fingers were the mates of those the baby lost. They looked and felt as if they too had been crushed.