These several years eight workers, six women engaged in vinyl shoe making and two men in printing factories died due to benzene poisoning in Osaka. Under these circumstances there has been tendency to use other solvents as substitutes for benzene. By such means the blood pictures of the workers have generally been found improved. On the other hand, cases of poisoning caused by other solvents, for instance carbon tetrachloride, tetrachloroethane, trichloroethylene, methyl acetate, methylethylketone, cresol and tetrahydrofurane, have been reported recently in many kinds of industries. Special features as to the use of organi^c solvents in recent times are as follows. 1) increase of the amount of consumption in industries. 2) spread of industries which use such solvents 3) tendency to use substitutes for benzene 4) increase of the use of mixed solvents In such circumstances we must pay attention to the next points for the health supervision of men handing organic solvents. 1) obscurity of separate components in many mixed solvens 2) variety of the toxic action of solvents 3) difficulty in diagnosis of psycho-neurological symptoms due to solvent poisoning Therefore, the following measures should be taken to overcome these difficulties. 1) recognition of the components of solvents; obligation of labeling, execution of analysis 2) recognition of the degree of exposure; determination of the atmospheric concentration, determination of the toxic substances and its metabolites in the blood, urine etc. 3) periodical medical examination; (examination of objective psycho-neurological symptoms is very important and for this purpose electrophysiological studies should greatly be promoted.)

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With a view to determining the role played by the use of low hydrogen type electrodes as a cause of metal fume fever, laboratory experiments were performed with 4 types of electrodes, including low hydrogen type electrodes, and the following results were obtained. 1) The mineralogical composition of coating materials was determined by microscopical examinations. One of the notable properties of low hydrogen type electrodes are the presence of such unusual minerals as CaF₂, ferrosilicon, a large amount of CaCO₃, MgCO₃ (in the form of dolomite) and water glass. 2) After experimental welding which was performed with different electrodes, on evidence of melting was found at the end of low hydrogen type electrodes, while the end of another type showed the evidence of melting by the heat of arc. 3) By the thermobalance method the author measured the change in weight during continuous heating and examined the timeweight loss curve at different firing temperature. The heating behavior of low hydrogen type electrodes was found to be quite different from another type. The heating curves of the former indicate (i) the maximum decrease of weight at 600°C (as a result of the decomposition of carbonates), (ii) a marked increase of weight (as a result of oxidation) by heating above 600°C, (iii) the definite loss of weight as a result of a high porosity above 800°C of the furnace temperature. The time-weight loss curve of the former also indicates high sensitiveness to the sudden change of temperature. 4) Definite heat absorptions at 500°C and 750°C and heat evolution at 600°C were observed in the differential thermal analysis of the low hydrogen type electrods. These properties were especially important as a cause of rapid destruction of the material. 5) The study of the microscopical structure of fired material by the low hydrogen type electrode was useful for ascertaining its high porosity after heating above 800°C. The principal features after firing are a marked decrease of the number of MgCO₃ particles, signs of dehydration of the water glass, and production of new round crystaline formation from the ferrosilicon particles which had originally irregular contours. 6) From the facts above mentioned the causative agents for metal fever might be attributable to the high emission of MgO particles in the dusts from the low hydrogen type electrode during the welding process.

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In order to clarify the behaviour of mercury in the blood, a mixture of ²⁰³HgCL₂ with human blood was prepared, and the distribution of mercury in the blood components and the state of mercury bound with blood corpuscles and with plasma protein were studied. The main results obtained are presented hereunder: 1) Distribution of mercury in the blood components: When the addition of ²⁰³Hg to the whole blood has been at a concentration of 10^-3M, more mercury is present in the blood corpuscle fraction than in the plasma fraction, and vice versa at lower concentrations than 10^-3M. The lower the concentration of mercury added, the less is the mercury present in the blood corpuscle fraction. 2) Mercury in the blood corpuscle fraction: The majority of the mercury is bound so weakly with blood corpuscles as to be readily removed from them on being washed with physiological saline solution. As a part of the mercury, however, can not be removed from the corpuscles on washing with Ca-EDTA solution instead of the saline, some amount of mercury may be strongly bound with blood corpuscles. 3) Mercury in the plasma fraction: Mercury in the plasma fraction is not bound with plasma protein and seems to be merely dissolved in the plasma fraction. 4) In vivo experiment: When the intravenous administration of mercury was done to the rabbits, the mercury in the blood decreased rapidly and the portion of mercury was more in the blood plasma than in corpuscles.

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