There are 15 known endemic fluorosis sources in the Pretoria district, and the fluorine concentrations in water in 10 of these vary from 1.43p.p.m. To 13.9 p.p.m. Chronic endemic dental fluorosis occurs in all these areas.
A general conception of a ""physiological cooling-ball temperature"" is given. After some remarks on the physical aspect of cooling-ball temperature and similar measurements, it is explained in detail how the cooling-ball temperature is particularly adapted to measuring the relationship between the human body and climatic forces.