In order to clarify the influence of injection of benzene and other organic solvents, weight of thymus and number of thymocytes of female mice of ddD strain were studied.
1. Among three groups of different ages, the numbers of thymocytes were decreasedby benzene injection, 2.0ml/kg, in a group of 8 weeks old and not in other two groupsof 4 and 6 weeks old.
2. Benzene affected more severely to the thymus of mice, who were bred under anatural condition, than those of mice under a controlled condition.
3. No significant change was observed in case of toluene injection and the resultswere equivocal in case of trichloroethylene injection.
4. As to the effects to the thymus, benzene was prominent in its property to decreasethymic weight and the number of thymocytes, but the mechanism to induce thesechanges of the thymus remained to be unknown.