THE "IRON INDEX" OF THE BLOOD

Among the most striking features of the blood is its content of erythrocytes, unique as carriers of the characteristic respiratory pigment hemoglobin. In designating the especial chemical peculiarity of this remarkable substance, students inevitably refer to the presence of iron in amounts quite unusual for other components of the body. Methods are in vogue for the estimation of all these important items of the blood; namely, the number of its erythrocytes, the content of hemoglobin, and the amount of iron present. Although quantitative estimations of the iron content of whole blood were probably made more than a hundred years ago, fairly accurate data have been available since the middle of the last century.¹

Somehow the use of iron determinations in blood has never achieved much popularity. Sherman² has pointed out that the amount of iron contained in the body is small—rather less than 3 grams, or hardly one-tenth