INFANCY. The term infancy is used vari ously by different writers to include a shorter or longer period of the earliest stage of human existence. By most writers it, is limited to the first 12 or 14 Months, extending to the 'time when the baby begins to walk and to talk, and so is synonymous with a in arms'; many medical authors would make it include the whole period of the first dentition, or up to about two and a half years. The characteris tics of the period are utter helplessness, rapid growth of body, gradual development of mus cular functions and great impressibility of the nervous system. In mankind this helplessness is' more marked and the Period of dependence is longer than in any other of the higher ani mals. It has been pointed out by John Fiske that the present elevation of above other animals is due largely if not entirely to this lengthened period of plasticity,— to his pro longed immaturity. Man is born with only a few of the lowest vegetative capacities fully'de veloped, such as digestion, respiration and cir culation ; the muscular and nervous functions are latent and only gradually develop; while the higher functions of the mind go on evolv ing until the fifth decade of life. A long in fancy or period of immaturity means a great capacity for development.
Birth and infant comes into the world with a fixed sum total of vital force, along with certain hereditary tendencies in development toward health and, perhaps, toward disease. These hereditary tendencies are all modified by the physical, social, intellectual and moral status of the child's family and surround ings: in a word, they are vastly influenced by the child's environment. Heredity was' for merly regarded as the most important factor in the child's life; but heredity is really only one of three great factors,— the others being the nutrition of the child, and his physical, intellectual and moral environment.' During the plastic years of infancy, childhood and adolescence, a bad heredity can frequently be overcome by proper management; on the other hand, the capital of a good heredity can be squandered. Nature always tends toward the normal or healthy, so that there is always the possibility for a bad to be obliterated if only the natural tendency is assisted. More then depends on the nutrition and environment of the infant than upon its heredity.
Nutrition: The best method of nourishing the infant is nature's way —to have it nursed by the mother. But for various reasons this is often impossible. Mod ern life—and especially city life—has in some way rendered a certain proportion •of women incapable of producing breast milk for their offspring. Every encouragement, however, should be given to the young mother; for it frequently happens that a second baby can be successfully nursed after failure with the first. Again, in not a few instances, the infant does not thrive upon the breast-milk, even though it may be abundant. In both these classes of cases some form of artificial or substitute feed ing is a necessity. Good wet nurses are so difficult to procure in the United Stafes that artificial feeding is generally preferable unless the baby is premature or feeble and failing: then the services of a wet nurse may be needed to save the infant's life.
Artificial or Substitute Feeding.— The best available substitute for human milk is an adaptation of fresh, clean unadulterated cow's milk. The milk should be diluted and other wise modified to suit 'the infant's feeble diges tive powers, and it should be givenpreferably, without being scalded orsterilized. In suriimei, or when there is any doubt as to the freshness of the milk, the cleanliness of the dairy or the eareful handling of the milk, or heating the food to a temperature of 155° F. is advisable. Details as to tnilk modification land Pasteurization can be found 'in any hook on *Infant Feeding.'* Ready-made infant' foods — the canned or' bottled proprietary foods not contain the' right ingredients for properly nourishing the infant, and their prolonged lat. elusive use is nearly always followed by some form of scurvy and rickets. These proprietary foods tontain large proportions of sugar or starch, and soy make' at babies, but such infants are generally pate, hale feeble powers of and are succumb to disease of the lungs or of the.di gestive tract. When the prepared infarct' fonds are used as additions to milk they . are :leSs objectionable, and may at times be of ad vantage and The infant that has been properly nourished before 'birth and is born at full term weighs on the 'average about seven and a half pounds-4-boya• being somewhat heavier than girls.