Effect of a pulsed magnetic field on healthy mice: a study of the weight of the thymus.

The hypothesis that magnetic fields act only on deficient functions has been tested through the weight of the thymus in mice. The involution of the thymus in mice is known to begin early in life. It is marked by a decrease in weight. Female Swiss mice of different ages were exposed to a pulsed magnetic field 0.6 or 6 mT in intensity, 12 or 460 Hz in frequency. It was shown that the weight of the thymus in 8-week-old mice was not modified by the exposure, while the weight of the thymus in 15-week-old mice was increased. The maximum increase, about 16% relative to the controls, was obtained 24 hours after a 30 minutes' exposure. Hydrocortisone or cyclophosphamide prevented the effect. The increase in weight has been considered to be due to an increase of the number of the cells in the thymus.