The average temperature of the infant is 100° F., but it is subject to many fluctuations. It is raised by ingestion of food, struggling crying, etc., and lowered by sleep, inactivity and insufficient food. Sponging with cool water or oiling the skin will frequently lower a high body temperature, which, if unchecked, might cause convulsions.
In man there are two sets of teeth. The first or temporary teeth are 20 in number, 10 in each jaw. The first tooth appears about the seventh month, the last about the 24th month. The dangers of dentition are much exaggerated. Well-nourished children of healthy parents cut their teeth earlier, easier and more regularly than do feeble children. If the first tooth is not cut before the 14th month there is some serious defect. About the sixth year (and before the temporary teeth are shed) the jaws contain all the temporary teeth and all the rudimentary permanent teeth except the wisdom teeth. At birth, when the teeth have not ap peared and in old age when they have disap peared the lower jaw is obtuse. During the growth of the teeth, the lower jaw increases in depth and length. To admit of these changes, the temporary as well as the permanent teeth should be taken care of and filled if need be. Food requiring mastication should not be given until there are several teeth. The permanent teeth are 32 in number, 16 in each jaw. The first one appears about the sixth year, the last from the 18th to the 24th or later. The thymus gland appears in the new-born, attains its full size by the end of the second year, then gradu ally diminishes until at puberty it has almost dis appeared. It is supposed to be one of the sources of the red blood corpuscles.
For the first few months of life tears and perspiration are rare. After three months they are freer. In rachitic infants perspiration is often profuse. Up to the end of the first year the sebaceous glands are very active, especially upon the scalp. The saliva and pancreatic juice are small in amount until about the third month and therefore starchy foods cannot safely be given to young infants. The gastric secretion at birth can as a rule readily digest the casein of mother's milk, but has difficulty in disposing of other food. Mucus in the infantile intestines
is copious, often ferments and may neutralize the feebly alkaline intestinal juices, and the pan creatic juice and saliva.
Both the small and large intestine are com paratively long, and digestion and peristaltic action are rapid. These facts, together with the small size of the stomach and the rapid growth of the body, require that the young baby be fed every two or three hours. The great length of the sigmoid flexure of the colon impedes passage of faces and induces constipation, which should be relieved by light laxative medi cines or, better still, by change in the diet.
The lymphatic glands are numerous and large in the infant and the communication be tween them and the general system is more marked than at any other period of life. They are readily congested and enlarged in affections of the throat, scalp, etc., and in scrofulous and syphilitic ailments.
The average weight of the male new-born child is 7 lbs. 11 oz.; of the female 7 lbs. 4 oz. For the first few days there is a loss in weight, then the weight gradually increases. Generally it is doubled by the 5th month and trebled by the 12th in breast-fed infants; in hand-fed, later. Usually a healthy child gains 20 lbs. in weight and 10 inches in height in first two years of hfe; in the third year four pounds and four inches. During next six years there is an an nual increase of four pounds and two or three inches; after the 10th year about eight pounds a year. About the ninth year in girls and the 11th in boys there is a diminution in the rate of growth, and at puberty (13th year in girls and 16th in boys) the activity of growth is the greatest. Between 12 and 15 girls grow heavier and taller than boys, but at 15 the boys again lead and maintain it through life. Growth usually continues to about the age of 25 in males and there may he a slight increase for 5 or 10 years afterward. Girls usually attain adult stature at about 21 years. Weight usually increases in the male and frequently in the female to the 50th or 60th year, due to an accumulation of fat.