The author studied the influence of a series of radioactive hot-spring baths, lasting 20 or 30 days, upon leukocyte functions in healthy male rabbits and in patients with rhenmatoid arthritis and other diseases. The radioactive hot springs used were "Hisui-no-Yu" and "Kenkyusho-sen" (the laboratory spring), both in Misasa Spa, the chemical compositions of which are deseribed in Table 1. The following results were obtained: 1) Wandering velocity of pseudo-neutrophilic leukocytes: When a series of plain water baths (41℃., for 5 minutes daily), were administered, velocity increased after the first bathing but later remained fairly constant, compared with initial levels, except for a temporary fall on the 9th day (Fig. 3). During the administration of a series of the weakly radioactive "Kenkyushosen" baths (43℃., for 5 minutes daily), it showed a slight increase during the first week, following a temporary fall after the first bathing, and a decrease during the third week, but it tended to
return to the initial level by the forth week (Fig. 1). In the course of a series of the radioactive ·Hisui-no-Yu" baths (40℃., for 10 minutes daily), it increased during the first week and tended to decrease during the second week, but returned to the initial level by the third week (Fig. 2). 2) Phagocytic ability for carbon-particles of pseudo-neutrophic leukocytes in rabbits: When plain water baths were given, phagocytic ability showed a rise on the third
day, after which it declined to the initial level and remained fairly constant to the end of the observation period (Fig. 6.). On the other hand, the phagocytic ability of the leukocytes in rabbits of the groups receiving radioactive hot-spring baths increased more and more markedly as serial bathing was continued, although it had slightly decreased immediately after the first bathing. The rise of phagocytic ability in the group bathed in "Kenkyusho-sen" was especially marked on the third and ninth days of serial bathing, and also on the tenth day after serial bathing had been discontinued (Fig. 4). This tendency was also observed in the group bathed in "Hisui-no-Yu", whose phagocytic ability was noticeable especially on the third and 14th days. The degree of the rise in phagocytic ability was demonstrably high in this group than in the former (Fig. 5). Acceleration of the phagocytic function of leukocytes in rabbits was observed up to the 40th day after the series of baths in the radioactive hot spring had been concluded. 3) From these findings. it is obvious that leukocyte function is increased by repeated bathing, but it should be kept in mind that a so-called dissociation phenomenon is present between the wandering velocity and the carbon-phagocytic ability of leukocytes in the groups bathed in hot springs: namely, wandering velocity showed a tendency to decline during the third week, while carbon particle phagocytic ability showed a marked increase during the same week. 4) In order to explore the effects of a series of radioactive hot-spring baths on leukocyte functions in patients with rheumatoid arthritis or other similar diseases (for example, back pain, fibrositis or neuritis), the author examined the wandering velocity and the phagocytic ability of neutrophils, and obtained the following results: The wandering velocity of neutrophils in patients with rheumatoid arthritis or similar diseases generally showed a tendency to increase during the adminlstration of a series of the radioactive "Kenkyusho-sen" baths at a temperature of 42～43℃. (Fig. 7). The carbon-particle phagocytic ability of neutrophils gradually increase from about the seventh day onward and reached a maximum during the second week, in patients with back pain, fibrositis and neuritis (Fig. 8a). In patients with rheumatoid arthritis, however, it declined temporarily on the fifth to seventh days in 3 out of 5 patients but thereafter increased gradually, reaching its maximum on the 20th day (Fig. 8b). Thus, the leukocyte functions in patients with rheumatoid arthritis are accelerated by serial bathing, but the response in some patients may be a decline of carbon-particle phagocytic ability during the first week. This is probably due to the stress bathing imposes on adrenocortical functions. It is believed, on the basis of the facts described above, that follow-up examinations of leucocyte functions can afford a better understanding of the effects of radioactive hot springs on the defence mechanisms operative in living bodies.