From clinical and pathological point of view, the causative agent of Minamata disease has been supposed to be an organic mercury compound and abnormally high content of mercury was detected in the fish and shellfish from Minamata Bay and in organs of cases of the disease. Then, what kind of mercury compound is contained in the fish and shellfish? In this paper, the biological and chemical properties of the toxic substance in the fish and shellfish was studied. The results were as follows:
1) The mercury in the shellfish from Minamata Bay, as it is, can not be extracted with water and organic solvents. But one third of the mercury in the raw shellfish is extracted with 3% NaCl solution at low temperature (2°C). The mercury in the NaCl solution is precipitated gradually with protein by salting out and dialysis, and all the mercury in the solution is precipitated with protein by heating at 63°C. It was proved that all the mercury in the shellfish was combined with the protein of the shellfish, including the mercury combined with simple protein, such as globulin and albumin.
2) From hydrolytes of the shellfish with alkali and acid, mercury is extracted with organic solvents. In the brain of rats administered with the extracted mercury, abnormal amount of mercury was observed, so the extracted mercury compound seems to be an organic form.
3) When the dry shellfish powder is digested with 0.04% pepsin solution of pH 1.6 at 37°C for 24 hours, one third of the mercury is tranferred to the digested fluid. When the extracted protein from the raw shellfish and the fish powder from Minamata Bay are digested with the same method, most of the mercury in the protein is transferred to the digested fluid.
4) By steamdistillation of these digests, almost all the mercury in the digests is transferred to distillates. The mercury in distillates was extracted with organic solvents. A cat was administered with the mercury compound in the distillate from the digest of the shellfish, and the abnormal mercury retention in its brain was observed.
5) But the mercury in the digest is not distilled at the temperature below 100°C with normal atmospheric pressure. And when pH of the digest is adjusted to neutral or alkali, no mercury is distilled by steam. No mercury is distilled by steam from the dry shellfish powder, as it is, or inorganic mercury compounds in acid solution.
6) The liver of a human autopsy case of Minamata disease and of a cat attached by the disease through feeding of abundant fish and shellfish from Minamata Bay, was digested by pepsin, and the digests were distilled by steam. Then a part of the mercury in the livers was transferred into the digests and the mercury in the digests was distilled by steam, and the mercury in the distillates was extracted with organic solvents. It was proved that in organs of human and animal cases of Minamata disease an organic mercury was accumulated.
7) The properties of the organic mercury compounds in the shellfish from Minamata Bay were compared with those of known alkyl mercury compounds. From steam distillation, solubility and stability in NaHSO₃ and NaHCO₃ solution, Rf value of paperchromatography and behavior towards ion exchange resins, the organic mercury compound in the shellfish is considered to be an alkylmercury compound, in the molecule of which has carbonyl radical or double bond.

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Generally speaking, cases of suicide are more frequent in spring and summer than in the other seasons. Therefore, the authors suspected some influence of the meteorological effects including atmospheric temperature and pressure etc. on the mental factor leading to suisidal attempts, and according to the investigation on the correlation between seasonal factors and the frequency of suicidal cases, the following results were obtained.
The monthly number of suicides was found to have a positive correlation to the monthly mean values of atmospheric temperature and hours of sunshine, and negative correlation to the atmospheric pressure, but no relation to the atmospheric humidity.
Attempts of suicide occurred frequently when the barometer indicated a pressure below the annual mean, and more frequently during the atmospheric pressure was dropping down, than during it was rising.
Unsuccessful attempts of suicide tended to be more frequent among females than among males. Suicide or its attempts among subjects below 20 years of age were far more frequent among girls than among boys.

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An investigation was made on the state of pollution of water in the port of Nagoya three times in summer. Samples for chemical and physical analysis were collected from the surface and the middle point of the depth at five locations in the port.
The result showed the ocean water made up a double layers according to the difference of the Cl-concentration. The grade of pollution at ebb-tide was greater than that of the high-tide. It was postulated that the auto-purification of the polluted water would be to some extent made at the half depth, but not on the surface. The principal factor of the pollution of ocean water was attributed to the polluted rivers which flowed into the port. The most polluted location was found where the river Yamazaki and Horikawa flowed into, and the location into which the river Oheflowed, followed the former. The ocean water for control at the out-side of the port was more polluted than anticipated.

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Hemagglutination tests as described by Boyden were conducted for the detection of antibodies against Sparganum mansoni antigen.
Human blood cells were sensitized with tannic acid and coated with the anigen prepared from dried Sparganum mansoni worm by sonic disintegration.
Antisera were obtained from the rabbit immunized by intravenous injection of the antigen.
The following results were botained.
1. It was shown that antibodies in the immune serum were successfully titrated by the hemagglutination test.
2. The optimum concentration of tannic acid for the treatment of red cells was 1:50, 000 dilution. Red cells treated with 1:20, 000 dilution of tannic acid showed often non-specific agglutination. The reactions were negative, when red cells treated with 1:100, 000 dilution of tannic acid were used.
3. It was observed that 1:3, 000 dilution of the dried antigen was the adequate concentration to sensitize tannic acid cells, and the highest dilution of the antiserum for positive reaction was 1:1, 600.

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The importance of glucuronic acid in the detoxication mechanisms has been widely recognized. The present experiments were made with rabbits which were exposed to carbon disulfide, benzol and lead, which are usually used in the today's Japanese industry. An exposing chamber for carbon disulfide was designed so as to regulate its concentration as high as 500ppm. The animals were divided into three groups and each group was exposed twice with a single exposure duration of 3, 6.5 and 12 hours. In order to induce lead and benzol absorption, the animals were injected subcutaneously twice with lead acetate solution, corresponding to 10mg/kg for lead and once with 176mg/kg of benzol respectively.
Analyses of urinary glucuronic acid and ether glucronide were carried out by the naphtoresorcin picrate method. The concentration of urinary glucuronic acid was corrected by the concentration of urinary creatinine. Thus the concentration of glucuronic acid was expressed as G/C ratio in urine. Principal results obtained were as follows.
1) After inhalation of carbon disulfide, G/C ratio in urine began to decrease rapidly and returned slowly to the normal range in about a week after cessation on inhalation.
2) The plasma cholesterol level and A/G ratio as well as GPT of the serum were little varied even after 12 hour inhalation of carbon disulfide. From these facts, it would be suggested that the decreased excretion of urinary glucuronic acid is not due to the impairement of the liver by carbon disulfide, but may be due to other, perhaps, neurological or endocrinological mechanisms.
3) The increase of G/C ratio in urine was found in the case of administration of benzol.
4) No change concerning the excretion of urinary glucuronic acid was resulted by administration of lead.

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