Mention was made, in the previous paper, of the fact that mottled enamel of the teeth results from the presence of fluorine in the water supply. The water of the city of Ankeny and surrounding territory may have a fluorine concentration to exceed eight or ten parts per million of water; mottled enamel is very prevalent in that area. Work by Smith (1) of the University of Arizona indicates that mottled enamel may result when the concentration of fluorine is as low as 0.8 to 0.9 part per million of water. The work of Schulz and Lamb (2) and McCollum, Simmonds, Becker, and Bunting (3) has demonstrated that sodium fluoride when fed to rats will produce abnormalities of the teeth of these animals similar to that generally known as mottled enamel in human beings. The work reported in this paper had as its object to ascertain if other inorganic fluorides will produce mottled enamel and also to determine if mottled enamel can be produced by organic fluorides. Furthermore, it was deemed advisable to ascertain if the administration of alum (aluminum sulphate) along with sodium fluoride would prevent the development of mottled enamel
