Our description of racial perpetuation should be finished by an account of the development of the fertilized egg. Snugly ensconced within the body of the mother, in an organ devoted solely to the purpose, the egg passes rapidly through the early stages, living at first on fats and proteins stored within itself. After these are exhausted it draws supplies from the body fluids of the mother. In the course of a few weeks it has developed its own conveyer system, with its own beating heart and its own stock of blood. There is never any actual mingling of the blood of the developing child with that of the mother; capillaries of the maternal circulation come into intimate contact with capillaries of the circulation of the child. Here interchange of all sorts of material goes on; food and oxygen pass from the mother’s blood to the child’s and waste materials from the child’s blood to the mother’s. During all this time the mother is eating, breathing, and excreting wastes for two. She cannot bring any nervous influences to bear on the developing child, since there is no connection between her nervous system and the child’s; she can, however, influence it chemically through the blood. Poisons that get into the blood of the mother can pass from it into the blood of the child. These may be the poisons of auto-intoxication, or drugs that the mother has taken. In either case they may do the child harm. We do not know very much about this, but it may be that a considerable percentage of children that are born with abnormalities that are not hereditary come by them through chemical influences received from the mother’s blood.
When the development of the child has gone far enough so that it can do its own breathing, feeding, and discharging of waste materials, it is expelled from the body of the mother in the process that we know as birth. This does not imply by any means that parental care and responsibility are at an end. Food, protection, and warmth must be provided. Education must be attended to, for the nervous system of the new-born infant is absolutely undeveloped. It has, through heredity, certain possibilities of achievement; their realization hinges upon the bringing to bear of worth-while influences. Upon the attainment of maturity the child will be expected to assume his place in society, and society has a right to the best that he is able to offer. In preparation for this it is the duty, both of the parents and of society itself, to provide throughout the formative years as nearly as possible the environment best suited to the development of those traits which make for usefulness. Environment cannot overcome the limitations of heredity, but environment can bring out the best that is in us.
CHAPTER XXI
CHILD AND MAN
EVERYONE is familiar with the beguilingly helpless picture the tiny baby presents. The disproportionately large head, with aimlessly rolling eyes and toothless mouth, the frail and delicate limbs, waving in the air or clutching spasmodically at anything within reach, the expressionless face, on which, for the first few days, only sensations of discomfort are registered, all mark a creature whose survival hinges absolutely on unremitting care; a far cry from the competent self-sufficiency of the average person of mature years. These surface marks of helplessness are by no means the most significant. Buried from view beneath the soft and velvety skin are characteristics of even greater meaning to those on whom falls the responsibility for the rearing of the new life.
At the time of birth the bony skeleton is very incomplete; there is a spot just above the forehead where the skull bones have not yet grown completely together, leaving a space where the brain is protected from injury only by the overlying skin. This spot can be detected easily in very young infants by its pulsations in time with the heartbeats. In most of the other bones the deposit of lime salts to which they owe their stiffness has gone only a little way, so that it would be impossible for the child to stand or walk even though it knew how. In this respect the contrast between the human infant and the new-born of such animals as horses or cattle is very striking, for the latter walk stumblingly from almost the moment of birth, and efficiently within a few hours thereafter.
Not only is the infant devoid of teeth, but in various other regards his digestive apparatus is undeveloped. Not only is he unable to chew solid food, but he could not digest most of it if it were served already chewed. During the early months of life the child is emphatically a one-diet being. His alimentary tract deals successfully with the mixture of proteins, fats, and sugars of which milk consists, provided the proportions are substantially those of mother’s milk and the quantity at a feeding is not too great. He can do this because the enzymes needed for digesting these particular substances are manufactured by his digestive glands from the very beginning, and because the muscles of his stomach and intestines can churn and propel the soft curd into which the milk is converted as soon as it enters the stomach. The fact that cow’s milk sets into a tough curd accounts for much of the difficulty some babies have in thriving upon cow’s milk.
There is no starch in milk, and neither the saliva nor the pancreatic juice of the infant contains the enzyme by which starch is digested. It is wholly useless to begin feeding starch-containing foods until this enzyme begins to be manufactured, which usually takes place when the child is about eight months old. Even then the introduction of starch into the diet should be gradual and cautious.
Modern science has discovered no better food for infants than mother’s milk, and no substitute more satisfactory in general than suitably modified cow’s or goat’s milk. Under modern conditions of life, particularly in cities where milk has to be transported over long distances, and where much time necessarily elapses before the milk can be placed in the hands of the consumer, there is serious danger of contamination of the milk with disease germs. In all enlightened communities this danger is fully recognized, and the entire milk supply, so far as possible, but that part of it destined for the feeding of children in particular, is safeguarded by all available means. A fairly reliable index to the degree of enlightenment of any community is the quality of the milk which its children receive. One recent discovery of considerable importance, and incidentally an interesting illustration of the way in which correct procedure may be hit upon in advance of the scientific knowledge which justifies it, is the finding that orange juice contains one of the dietary accessories, known as vitamines, essential to health, and present in raw milk, but destroyed when milk is heated. For years, physicians had recommended orange juice for babies. It is of vital importance when the milk must be pasteurized.
Both the heartbeat and the breathing in the young child are much more rapid than in the grown person. It is believed that this quickness of heart action and of breathing rate are related to the smaller size of the infant as compared with the adult and are of no very marked significance. At any rate it is true in general that the smaller the animal the more rapidly does its heart beat and the more quickly does it breathe. A very noticeable fact about young children is the susceptibility to all sorts of influences of the mechanism by which the breathing is controlled. Every passing interest reflects itself in heightened breathing. Violent emotion often leads to such extreme overbreathing as to drain the child’s blood of considerable of its store of carbon dioxide, whereupon the rapid breathing gives place to prolonged holding of the breath. Many a young mother has been seriously alarmed by the length of time her offspring in a tantrum is able to refrain from drawing its breath. Contrary to the appearance of things, which would indicate that the child is holding its breath out of spite, and in the hope of getting even with its parent, the cessation of breathing is largely or wholly automatic, indicating the way in which nervous and chemical influences have interacted to suspend the respiration.
The child is born with all its muscles in place, and all fully formed in that every muscle fiber the child will ever have has been produced previous to birth. In fact, as soon as the full equipment of muscle fibers has been laid down the body loses the power to form more, so that if, through injury, one is so unfortunate as to have some of his muscle fibers destroyed he will have to get along for the rest of his life with those that are left. The gaps in the muscle tissue that are produced by injuries are filled up by a kind of connective tissue known as scar tissue. The muscle fibers are all present, but smaller and weaker than they will be later.