The relative sizes of the various organs of the body of an infant are very different from those of an adult. If the relative sizes of the child's body were retained throughout life his head would be as wide as his shoulders and his legs those of a dwarf, while all parts of the body would be out of proportion. Such an adults would be a monstrosity.
Each organ of the body has its own ratio of growth and its own period of development . There is not alone a definite period, of the child's life for the cutting of its teeth, but there is also a definite period for the development of certain of its brain cells; and a definite period for sexual development.
The process of growing is never haphazzard although the child grows in one direction this year and in another direction the next. The child's heart increases in size twelve times before adulthood is reached, while the aorta, the body's largest blood vessel, increases only three times. The liver of the child is equivalent of 1/18 of its size; the liver of the adult, 1/36 of the size of the body. In early childhood the stomach is vertical and tubular; in the adult "bean-shaped" and more or less horizontal. The six year old child has sixty per cent more body surface in proportion to weight, than has the adult.
In babyhood the bones are largely soft cartilage. As age advances and ossification advances the bones become harder and stronger. The child must gradually learn the use of its various muscles, even those of the eyes. It is unable to execute complex movements, but must gradually acquire this ability.
The infant and child possess less red corpuscles and more white ones than the adult. There is greater activity of the Iymphadenoid glands of the infant and child than of the adult. Its reactions to infections is much more prompt and vigorous.
Medical authorities tell us that a baby can usually hold its head up unsupported at about three months. If a child can't hold its head up unsupported at three weeks, at the latest, that child is not developing well.
The amount of hair with which children are born varies. Some children are born with a luxuriant growth, others are almost bald. This hair is usually, though not always, lost during the first months of life, and is followed by a new growth. The hair may change in color three or four times during the first three or four years of life.
Almost all children of the blond races and of some of the darker races, like certain of the hindoos, are born with blue eyes. They usually begin to assume their permanent color during their first few weeks. There is no foundation for the theory, preached by some, that brown eyes are the results of physical deterioration. It is asserted bv one of these "iriologists" that, "The eyes of people living in the south become brown because the actinic rays of the sun, as well as the heat, break down the protoplasm of the cells, which are albuminous and all proteins and albumens give off hydrogen-sulphids which is a poison, and which is not eliminated as quickly as it is produced by the broken down tissue." This hydrogen-sulphid resulting from the cooking of the flesh of Southern people is supposed to stain their eyes brown and we are told to "change the diet of brown eyed people, stop giving them heavy actinic ray and heat treatments; give them the proper adiustments and within 3 to 6 months their eyes tell the story of elimination, for they become lighter in color." This is rank nonsense without a single demonstratable fact to support it.
The brown of brown eyes is a pigment deposit (like the "tan" in the skin), in the stroma of the iris. Where the stroma is devoid of pigment, the purple pigment layer, resting on the basement membrane of the iris, shimmers through the stroma as a uniform. clear sky blue.
A baby can see at birth--far sightedness being normal sight. They are thought to begin to recognize objects at about 6 to 8 weeks and to focus their eyes on objects at about 3 months. Up to this age the average child has some difficulty in fixing its eyes and may appear slightly cross-eyed, or present some other evidence of muscular incoordination of the eyes. Babies seldom shed tears in crying before they are three months old.
Strong light is supposed to cause the eyes of babies discomfort However, the closing of the eyes, when a strong light is thrown on them, is a reflex act produced by thc light striking the eye-lids. The eyes are not sensitive to the light.
Babies can hear at birth but they hear little during the first few days and learn to recognize where a sound comes from at about two months.
They are supposed to have a very poor sense of smell, while their sense of taste is not very acute at birth.
Babies will smile at about six weeks and will laugh aloud at about the third to fifth month. They learn to "coo" at about three months.