Refractometry is yet an almost blank chapter in pediatrics. In contrast to the now numerous papers on refractometry in adults, such researches in children are rare.
On normal refractometry of blood serum in healthy children we know only the papers of Reiss1 and Nast.2 According to Reiss the refractometric index of blood serum in nurslings is lower than in adults, and this decrease agrees with about a 2 per cent. lower concentration of serum proteins. From the age of 6 to 10 months, says Reiss, the refractometric index rises and attains a definite degree, with a value varying from 1.3480 to 1.3514, as in adults. Refractometry is perhaps the best and surest means of serum protein estimation; Reiss's researches on the subject are too well known to need any detailed mention here.
In order to estimate protein concentration in blood serum, we subtract from the number read 1.33320,