The author investigated the effect of radioactive hot spring bathing on serum iron values. The serum iron values were measured by Umemoto-Yamamoto's method using o-nitrosoresorcin monomethylether, as a colour-developing reagent. The chemical compositions of the spring water used is as following: pH : 7.04, Rn : 38-151x10(-10)curies/l, K(+) : 14.0, Na(+) : 540.2, Ca(++) : 61. 2, Mg(++) : 6.6, Fe(++) : 89.0, AI(+++) : 0.1, Cl(-) : 709.5, S0(4)(--) : 179.5, HCO(3)(-) : 226.7, H(2)SiO(3) : 89.0, HBO(2) : +, CO(2) : 29.5, totaling 1,827mg/kg. 1) Single bathing: The iron values in the serum were measured before and after 0, 1/2, 1 and 2 hours after the radioactive thermal bathing for 10 minutes in water of 41 ±2℃ in temperature. Single thermal bathing showed no significant effect on the serum iron values in healthy hnman subjects, but the serum iron concent:'ations in healthy white rabbits tended to decrease following single thermal bathing and to remain at a decreased level for 1/2 to 1 hour, and returned to normally within 2 hours from the time of the bathing (Table 1, 2 and Fig. 1, 2). 2) A series of baths: The author examined the serum iron values of patients with rheumatic disorders before and 3rd, 7th, 14th, 21st and 28th days after in the course of "a series of baths" in radioactive hot spring. Patients bathed in water of 41 ± 2℃ in temperature, for 5-10 minutes, 2 or 3 times daily. A fall in the serum iron values was seen on the 3rd to 7th days. At that time the pattern of iron absorption from intestine showed a iron dificiency anemia type. The rate of absorption of iron was rapid. At about the 14th day, the serum iron values of patients tended to increase but unbound iron-binding capacity of the serum decreased. Subsequently, the serum iron values returned to the initial levels between the 21st
and 28th day (Table 3, 4, 5, and Fig. 3, 4, 5), 3) It is said that the reticulo-endothelial system plays an inportant part in iron metabolism. The author injected 5 ml of Indian ink into the aural vein of rabbits for the purpose of blocking the reticulo-endothelial system. These procedures were carried out once a day for 7 successive days. The rabbits with "a blockade of R. E. S." had no significant change in the serum iron values during a series of baths. From what has been stated in the above, it may be said that bathing in radioactive hot springs regubtes the iron metabolism of patients with anemia and brings about the acceleration of the medullary function.