From the above statement it can be seen why one with exhausted nerve cells should avoid exercise. The nervous system should be at rest. For example; if a youth is recovering from some severe illness――typhoid fever, let us say――he should not at first try to get back his muscular strength by self-exercise. The muscles need blood sent to them to grow and regain their former elasticity, but the nerve cells required for all this must have a rest. How is it to be done? By the exercise of another person’s nerve cells. That is, the muscles should be massaged by some strong man. As the nerve cells gradually come to their full activity again, then the youth may commence gradual exercises on his own account. It is the general impression among athletes that exhaustion and “loss of wind” are due to the inability to consume sufficient oxygen and exhale rapidly enough carbon dioxide. When the muscle is moving rapidly and forcibly, it is true that it demands more oxygen and gives off to the blood more carbon dioxide than when at rest. When a man is running as fast as he can make his limbs move, he is able to keep up the pace but for a short distance, unless, like the hunted hare, he runs to death. On account of the forced and rapid muscular action in this case the poisonous materials are thrown into the blood, to be carried to all parts of the body――muscles, nerves, brain. The heart is affected by this poison through the nerve cells controlling this organ; the muscles of respiration are similarly disturbed. The panting, distressed efforts of breathing, sidelong tumbling and final semi-unconsciousness of the hunted stag or hare are good examples of acute self-poisoning ending in death. It is just as much a case of poisoning as would be a case of gas poisoning; the only difference being that in the first case the gas is manufactured in your body, in the other case, outside and you breathe it in.