In the preceding paper Behnke, Feen and Welham1have emphasized the value of the specific gravity of the body as a whole as an index of obesity. In their investigations a high value of 1.081 was associated with an average weight of 148.7 pounds (67.6 Kg.), while the corresponding weight for a group having an average low value of 1.056 was 176 pounds (80 Kg.). If obesity and not weight per se is the chief factor tending to produce low values for specific gravity, then conversely a group of heavy but lean men should possess a high average value for specific gravity. It was of considerable interest, therefore, to make a study of professional football players, the majority of whom had been selected for "all American" football teams. Essentially it was found that, although the average weight of these men was 200 pounds (90.9 Kg.), the average specific gravity