Daily loss of calcium and sodium from the skin of two healthy men.

1. The daily losses from the skin of Ca and Na have been measured for two healthy men. The losses included Ca and Na in exfoliated skin cells as well as in insensible perspiration. The daily output of Ca in urine was also measured.2. In five measurements, the total daily skin loss of Ca ranged from 8.0 to 21.1 mg with mean values of 16.7 and 10.8 mg for the two subjects. The total daily skin loss of Na under the same conditions ranged from 45 to 146 mg with mean values of 97 and 77 mg respectively.3. The ratio of the daily skin loss to the urinary excretion of Ca was 6.8 and 3.4%.4. There was no correlation between the daily skin loss of Ca and atmospheric humidity.5. In the last experiment, the fraction of the total skin loss of Ca due to fluid secretion was assessed by giving an I.V. dose of (47)Ca to each subject. The values derived for this fraction were 0.37 and 0.38.