Calcium exists in the blood serum in three forms in an ionized state, in an un-ionized but diffusible or dialyzable form and in an un-ionized, nondiffusible combination.1 The evaluation of the part played by these fractions in the body metabolism is not fully understood. One of the underlying reasons for this failure to evaluate the rôle of these fractions properly has been the lack of standardized methods for their determination, and consequently insufficient data as to their normal values. Several studies on the diffusible serum calcium in animals and in human adults have appeared,2 but it is our belief that no work has been done that deals with normal values for the calcium partition in the new-born infant.
METHODS AND EXPERIMENTAL PROCEDURE
Observations were made on fifty normal new-born infants, ranging from 5 to 22 days in age. Of this group, twenty-four were boys and twenty-six girls. Blood