TABLE
| In the first month, about | 1.00 per cent |
| At the middle of the first year | 0.30 per cent |
| At the end of the first year | 0.15 per cent |
| At fifth year | 0.03 per cent |
| Maximum in later years for boys | 0.07 per cent |
| Maximum in later years for girls | 0.04 per cent |
Retention of Nitrogen in Infancy.—When the baby is gaining in weight and strength there is a retention of both nitrogen and salts, and when the baby is not gaining there may be a loss of both of these bodies; when one is retained in the body the other is apt to be retained.[65]