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.
The toxic effect of nitroglycol upon the heart functions was investigated electro-cardiographically using rabbits injected subcutaneously with the poison. On the electro-cardiographic patterns thus obtained, some changes such as depression of ST, negative, low, and biphasic T were noticed by comparison with those obtained before the administra-tion of the poison, and these changes occured independently to the amount of methaemo-globin formed in the blood. The changes on the patterns disappeared at 24 hours after the injection, but when the poisoned rabbits were examined by the anoxia test method, the abnormal patterns above mentioned appeared again. This fact indicates that the effect of nitroglycol upon the heart tissues or the heart functions remained still, whilst no traces of nitroglycol were noticed in the blood. From these findings, the changes on the patterns of poisoned rabbits were assumed to be caused by the direct action of nitroglycol upon the heart functions.
In Yokkaichi-city, where power stations, oil refining and related chemical plantsexist, growing number of cases of asthmatic patients has been reported since these plants were put in operation in 1955. At Isozu, where air pollution is most severe, incidence of asthma reached up to 2.5% of total population in 1964. In whole Yokkaichi-city, annual average of sulphur dioxide level by lead peroxidecylinder method in each district is well propotional to the incidence of "asthma". Furthermore, at Isozu, incidence of asthma attack in each patient is closely correlated to weekly average concentration of sulphur dioxide. Clinical features of "Asthma"have been described.
The protecting effect of the porous elastic materials inserted between the hand and the vibration source was examined by using the driving point mechanical impedance. This paper reports the results obtained with two types of polyvinyl chloride foam, whose shape was the cylinder of 5 cm diameter. One of these two types was found to be available above 30 c/s as the vibration protector. The measuring method of this damping effect was also examined with the mechanical model of the hand.
The dynamic visco-elastic properties of the porous elastic materials were measured by impressing the compressive vibration and were translated into the electrical equiva-lent circuit through the mechanical one consisting of four elements. The human hand was also simulated to the electrical equivalent circuit. Consequently, by using the simulator, the author examined how the thickness of the porous elastic materials influenced the protection effect. The porous elastic materials in this study were two types of polyvinyl chloride foam (described in the previous paper). From this experiment, it was concluded that the protection effect was proportional to the thickness of the porous elastic material in the frequency range between 30 c/s and 400 c/s.