What is the explanation of longevity in Huangdi Neijing?

The hundredth day after a baby is born is the first birthday of a newborn baby, not the date of birth a year later, but the hundredth day after birth, commonly known as "centenary", which means wishing the child a long life. On this day, the baby will receive gifts from the elders. The older the elder, the greater the blessing the baby gets. Giving a baby a hundred days is an ancient custom of the Chinese nation. Please celebrate with friends and family and wish the baby a healthy growth and a long life. Children 100 days, the host family invited midwives, relatives and friends to dinner. Generally, eating eggs means "perfection"; Or eating noodles means "longevity". This kind of activity is commonly known as "one hundred years".

Shave the baby's head, especially the boy. In the old custom, when a boy is over 100 years old, his parents ask the barber to shave off the child's hair, leaving only a tuft of hair at the lower part of the back of the head. This is called keeping a hundred-year-old hair, which means wishing the child a long life. When the baby is over 100 days old, the bride's family gives a hundred steamed buns, which is called "steaming (increasing) centenarians" and a hundred dollars, which is called "centenarians' money". When the baby is born for a hundred days, it is necessary to give the baby salt, commonly known as "taste". Parents buy pig intestines, pig bellies, pig kidneys and pig livers for their babies, and cook porridge for their babies. Commonly known as "filling the stomach". After children "fill their stomachs", their digestion is very strong and will be strong in the future. After a hundred days, babies will not die so easily. "Hundred" can be associated with auspicious things and hopes such as longevity.