GROWTH AND DEVELOPMENT OF THE HUMAN BEING. In this article growth refers to an increase in size, and de velopment to an increase in capacity. The body begins in a microscopic cell, and passes through the various stages of birth, growth, develop ment, decline, and death.
The life of an individual may be studied in various periods, the embryonic and foetal (which do not concern us at this time) and those of infancy, childhood, youth, maturity and old age. The above division is convenient, but not physi ologically exact. The various periods are not sharply limited. From birth to maturity, with a gradual increase in size of various organs, there are progressive modifications of func tions. Toward old age, decline begins and the modifications retrogress.
The Period of Infancy is variously limited by different writers, extending from birth to the end of the fourth, fifth, or even the seventh year, the last considered by law as the begin ning of responsible life. Probably the best lim itation is from birth to the end of the first dentition, about the end of the second year. At birth, connection with the mother suddenly ceases, and a new existence begins with the first inspiration. Then the vegetative functions, digestion, circulation, respiration, secretion, ex cretion and assimilation, are soon established. The infant performs all the functions of adult life except reproduction and volition. But in order to have them at their best they should be intelligently supervised by the parents. The young baby is the most helpless and dependent of all creatures. The care it receives influences its future life. With no care it must perish.
The period of infancy is characterized by frailty, active nutrition, rapid growth, and com mencing development. It is especially prone to convulsions from improper food, or from high body temperature, whatever the cause, to rickets and scurvy from improper nourishment, to spasmodic affections such As false croup, to hydrocephalus, meningitis, whooping cough, diphtheria, diarrhoea, bronchitis, pneumonia, and to the eruptive diseases, measles, chicken pox and scarlet fever.
The rate of infantile mortality is very high.
From one-fourth to one-half of the children born in our large cities die within the first year; in small towns and in the country the rate is much lower Many of the new-born are en feebled by vices of formation, such as cyanosis, spina bifida, hydrocephalus, or meningocele, by an hereditary syphilitic, scrofulous or tuber culous taint, or by chronic affections in the mother. All infants are exposed to the risks of an improper dietary, impure air and the ex tremes of heat and cold.
The bones of the infant are very vascular, quite elastic, have but little firmness, and their epiphyses are cartilaginous. They are there fore readily inflamed, as in scurvy, may be dis torted by pressure, or incompletely broken by apparently slight injuries, or the epiphyses may be separated by such injuries. To forcibly lift a young child by one arm is always dangerous. The slcull at birth is not fully ossified and can be readily compressed. The anterior fontanelle begins to close about the 9th month and is usu ally closed about the 18th. Depression of this fontanelle is one of the evidences of general debility. Premature closure of the skull is a cause of epilepsy or idiotism. The vertebral column is straight, lacking the curves of later life, and is quite flexible, but this flexibility tends to backward, forward or lateral distor tions of the spine, as the result of rickets, in flammation (caries) of the vertebra, or of sit ting, standing or reclining in strained positions. Allowing infants (especially feeble ones) to sit, stand or walk too early tends to produce bow legs and knock knees, as well as spinal deform ities. It is many weeks before a baby can hold up its head. Even by the 12th week it is not properly balanced. It may be at the 16th. The first attempt to sit is about the 16th week, and sitting is accomplished about the 40th. About the 38th week, the child attempts to stand, and should be able to stand alone by the 11th or 12th month, and to walk unaided by the 15th or 17th month. Some children never creep. If they do, the attempt is made•about the ninth month.