Shakespeare speaks of the seven ages of man, but from the medical point of view man has been considered in three periods: childhood, when we practice pediatrics on him; the grown-up stage, when we have no special term for our procedures; and old age, when we now say that he is a candidate for geriatrics. But as Sir Thomas Browne points out, and as we are told that the Chinese reckon, we are nine months old when we are born. In many respects these nine months are the most important portion of our life, for we are then being formed in a pattern which cannot change.
The best you can do for the child during the first nine months in the moist climate of the mother’s womb is to take good care of this parent. If all goes well with her, the chance of a satisfactory child developing is as good as is anything desirable in this world.
There is no great transformation when the baby is born. It just seems so because of the spectacular aspects of birth. He still needs to receive oxygen and give up carbon dioxide, but he uses his own lungs instead of his mother’s; he prepares his own food in his digestive tract from now on; and for the first time bacteria begin to grow in his intestine, which has previously been sterile. How difficult to distinguish our friends from our enemies! We view bacteria with fear, yet evidently these intestinal ones have rushed to our aid. Later in life we find that these beneficent inhabitants of our alimentary depths may be persecuted by the wonder drugs just as the wicked bacteria are. The balance of nature has to be maintained here as in the great outdoors.
The baby’s skin has been secreting a fatty waxy material and continues to do so after birth. The kidneys have already been secreting urine. Of course the muscles, including the heart, have been working. Whether the baby has been thinking I will not pass upon, but up-to-the-minute psychologists have suggested that he has been. In fact, the birth of the baby merely modifies, in a continuous sequence, his bodily functions. One of the chief wonders of our incredible body is the unostentatious way in which it adapts its activities as needs arise.
In our second age of man, a combination of Shakespeare’s infant, “mewling and puking,” and his schoolboy with “the shining morning face,” I would say that the emphasis is on growth rather than development, though, of course, there are changes other than mere increase in size. In my youth, for example, I had the pleasure of knowing a young woman who, presumably because of some change in her pituitary gland at the age of three, had ceased to grow in stature. Later she was a beautifully proportioned and unusually keen-minded adult, whose only lack of development was in her size. Otherwise she had progressed as all normal children do. It is our bones that largely determine our size. Not until a little over a half century ago, when Roentgen discovered the X-ray, did we realize how the bones grow from centers of cartilage which we often cannot see at first, and that some of these centers have not finished their work even when the person has reached puberty. Adolescence, the period between puberty or sexual maturity and the time when the individual has achieved the wisdom to vote, does not mark but accompanies the final change in stature. But this period signifies little, for Goethe said that man is a perpetual adolescent. The years from birth to the voting booth are the formative ones, but we are pretty well equipped before we start these, as the primitive functions necessary to keep us alive have been laid down, with the sympathetic nervous system in command.
Yet we learn to assume some partial control over even these primitive functions. Breathing we can stop for a while, or hurry up. Our bowels and bladder we learn to take charge of. On the other hand, the infant is born with the instinct to milk nourishment from a nipple, using for this purpose muscles in the cheek which will later waste away with disuse. Once lost, this valuable function cannot be acquired again.
The use of most of the voluntary muscles becomes automatic, particularly the ones with which we acquire skills. As age advances, the acquiring of new muscular skills becomes more and more difficult. However, a few people with inherent dexterity seem to belie this rule. We cannot generalize accurately about adolescence either of the body or of the mind. We see boys who are giants on their school football teams or precocious intellectuals like Thomas Babington Macaulay, who, when a few years old, could recite Scott’s Marmion and knew several languages. But a few exceptional cases prove little. The progress of the great majority of us can be charted in advance.