Each baby's birth should be recorded by the registrar of births, and parents should make sure that registration has been attended to in the city or town where they live. In some states birth registration is already obligatory, but in any case it is required by the child's own interest. For instance, in later life it may be necessary for him to prove the date and place of birth in order to establish, among other things, his right to vote and to inherit property, and to settle the question of his liability to military service. Moreover, complete and accurate birth registration is needed by every community because it is essential to such reforms as reducing infant mortality and abolishing child labor. GROWTH AND DEVELOPMENT Statements in regard to growth and development are based on observations of many children. It should be remembered that the following figures represent averages only, and that healthy children may vary from them considerably without giving cause for alarm. AVERAGE SIZE.--The average weight of a baby at birth is from 7 to 7½ lbs. and the average length is about 20 inches, but it is not unusual for a child to weigh anywhere from 5 to 10 pounds at birth and to measure from 16 to 22 inches in length. During the first week of life a baby loses slightly in weight. After the first week a healthy baby should gain from 4 to 8 ounces a week until he is six months old; after that time the weekly gain is less. The weight at birth will usually double during the first five months, and treble during the first year. Consequently, a baby weighing 7 pounds at birth may be expected to weigh 14 pounds when five months old, and 21 pounds when a year old. Weight is one of the most important indications of a baby's condition. He should be weighed every week during the first 6 months, once in two weeks during the second 6 months, and once a month throughout the 2nd year. MUSCULAR DEVELOPMENT.--A baby at birth is helpless, and during the first few months he has little muscular control. During the third month he ordinarily begins to lift his head, and he can usually hold it up without support by the time he is 3 months old; when 7 to 8 months old he sits erect and begins to play with toys. From this time a baby makes rapid progress; he attempts to stand on his feet, begins to creep, and by the time he is 14 months old he is usually able to stand alone, or even to walk a few steps. He is usually running about without difficulty when fifteen or sixteen months old. Babies should never be urged to walk or to bear their weight on their feet. If healthy they are generally eager to go about unaided, and like to investigate their surroundings without assistance. If walking is unusually delayed, a physician should be consulted.