Editor’s Note: This issue’s classic is the early paper by J. B. Boussingault on his realization of the relationship between iodine that was naturally in the diet and the presence or absence of goiter and cretinism in an indigenous population. In this instance, the location was New Granada (a part of which is now Colombia, South America), and the people affected were the Indians who worked in the silver and salt mines in that area. The iodine came from the oily fluid mined with the salt and was easily detectable. He could not detect iodine in the drinking water itself; by analogy with the undetectable amount of iodine in sea water, yet which must still be there, Boussingault reasoned that the Guaca drinking water contained iodine as well (the starch method used then to detect iodine was not a particularly sensitive assay). As noted in this issue’s Historical Note, he recommended iodine prophylaxis to prevent goiter and cretinism about a century before it became common practice. The classic is a partial translation of his paper in the Annales de Chimie et de Physique 1825;30:91–96.