Exactly how old is "old"? At what precise spot on the calendar does youth end and old age begin? We've all seen automobiles of "vintage" dates whose owners give them such careful, loving treatment (far more careful, in most instances, than they give their own bodies) that these conscientiously shined-up old buses perk along merrily for years. While it's true that these venerable autos don't have quite the same dash and class as today's sleek models, yet, ironically enough, there are not infrequent occasions when these antique models are seen blithely chugging past their streamlined and stalled mechanical descendants.

Then we all know the fellow who buys a handsome new car—all bright paint and shiny chrome—and has it looking and running like a wreck in six months.

So there you have it—one car still in service and going strong despite the many, many years of license plates that have adorned its out-of-date chassis; and the other car, not a year out of the factory, ready for the junk yard. The same thing holds true for the human machine. The sluggish, half-alive person who moves through each day with no more effort than absolutely necessary, for all his scant twenty, thirty or forty years on this planet, is literally older than the peppy man or woman past forty who wakes up each day with a genuine interest in what life is to hold for him or her in the next twenty-four hours.

Have you ever given any serious thought to the difference between living and being alive? That section of living tissue from a chicken heart kept for a number of years in a jar by the famous Dr. Alexis Carrel was not alive—it did not run about the barnyard, enjoying to the fullest its God-given faculties as a chicken. Likewise, the man in a coma lives, but he is not alive.

Staying young means living with vitality, in a body surging with power and energy, and with a mind tuned in to the vital principles of happiness.

If you're not alive to all the powers that are yours as a living, thinking human being, then something is wrong with the chemistry of your body. You probably know several per­sons of your same age who are far more alive and youthful than you are.

The psychologist would probably say that this difference in the ability of two persons to remain keenly alive to their surroundings and to their possibilities is a matter of "indi­vidual temperament." But I say that it's primarily a matter of body chemistry.

So-called "temperament" is chiefly a question of how well or how poorly your endocrine glands function. (More about them later as they enter into your eat-and-grow-younger pro­gram.) And the efficiency with which your endocrine glands function—or do not function—depends almost wholly on the food chemicals you provide for their intricately vital work.

That is why the sluggish person, of whatever age, who moves through each day with about as much energy and vitality as a snail in its shell, is probably killing his own pep every time he opens his mouth to drink or eat.

"Getting old" is not a matter of calendar years any more than growing older presupposes becoming senile.

Read that sentence again. It contains the concentrated wisdom of this entire book. It might well be made into a motto placard, to be hung where you could read it several times a day and ponder its truth.

Senility is pathological (diseased) aging. Senility is a break­ing down of body, mind and spirit. Senility has no relation to the number of years that have elapsed since a person was born, because senility has actually been noted in persons still on the "safe" side of forty.

Premature old age is a disease—a deficiency disease, as real as pellagra, scurvy or any other human ailment arising from an imbalance in body chemistry.

What causes this imbalance in body chemistry? Improper diet, usually. When is a diet "improper"? When it fails to supply constantly and adequately the food materials needed to keep your body tissues in good health. You may be sure a diet is "proper" if it is expressly planned to keep the tissues of your vital organs (heart, kidneys, lungs, brain, intestines, liver) healthy and in good repair, and to provide all the ma­terials needed by your endocrine glands for manufacturing their invaluable hormone secretions.

Then, with plenty of tissue-repairing and hormone-stimu­lating food in your meals each day, your body chemistry will be in balance, provided you don't also eat food that clogs up the system and denies adequate nutrition to your vital organs.

"But how will I know whether my diet is proper?" you ask with good cause.

That is where your Eat-and-Grow-Younger program enters. Every part of that program (see Part II) has been carefully planned to give you a proper, though still appetizing, diet which will nourish your endocrine glands and keep the tissues of your muscles and organs from becoming prematurely "worn out."

The chemical laboratory of your digestive tract converts the food you eat into still other, more readily usable food chemicals. You may not think of that sirloin steak, green salad and cup custard you had for dinner as being "chemi­cals." But by the time those items reach your bloodstream, all resemblance to the food as you last saw it has disappeared. The steak, the greens and the custard have been converted, in the laboratory of your digestive tract, into the food chemicals needed by the living, breathing cells that make up your body.

We often speak of the human body as a "machine." Yet, actually, your body is more than a machine—it's an extremely complex laboratory where intricate chemical reactions take place which no human chemist has ever been able to dupli­cate.

The awe-inspiring thing about this mysterious body o£ yours is that when some "mechanical" part breaks down, more likely than not under ideal conditions your "chemical laboratory" can rush quickly produced substances to the spot that needs repairing, in order that life may go on and the body's efficiency not be seriously impaired.

You'll notice I said that "under ideal conditions" the chemical laboratory in your body can produce quickly those mending substances needed to put injured or worn-out body parts back in good working order.

What are those ideal conditions?

First, certain "test tubes" (the endocrine glands) must be in proper working order.

Second, enough of a certain food element known as pro­tein must be provided the body's chemical laboratory, not only to keep the glandular "test tubes" themselves up to par, but also to rebuild constantly wearing out cells throughout your entire body.

These, then, are the ideal conditions under which your body, at any age, is given the power to renew your youth and prolong your vitality: Endocrine glands in good working order, and an abundance of protein in the daily diet.

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