Dusts of various silicious compounds, such as muscovite, chlorite, tourmalin, beryl, topaz, wallastonite, talc, epidote, orthoclase, diopside, yttrialite, bustamite and gadolinite as well as those of alpha-quartz and coal were prepared in size of three microns and less, and they were ascertained of their purity through the X-ray diffraction method. Each of these dusts, in amounts of 10 mg and 50 mg respectively, was introduced into the trachea of rats, and changes in the lung and thoracic lymphatic glands were examined two, four and six months after the introduction. In the case of talc dust, although formation of glanulomatous nodes in the lung was marked, that of fibrosis was not confirmed, and changes in the thoracic lymphatic glands were very slight. In cases of silicates with radioactivity (yttrialite, gadolinite, and bustamite), fibrogenetic changes were observed in a wide field of the lung, and slight fibrosis was confirmed in the thoracic lymphatic glands. Dusts of epitode, which contained alpha-quartz in 36 per cent, caused slight changes of silicosis. Dusts of other silicates, in general, introduced in an amount of 10 mg, caused merely changes similar to those by coal dust, while through introduction in an amount of 50 mg most of them caused strong fibrogenetic changes, especially muscovite and biotite. In these cases, changes in the thoracic lymphatic glands were rather more marked than those by the coal dust, but they were not of such typical fibrosis as found in the case of alpha-quartz.

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One of the authors had previously proved in the experimental study on lethal time of mice that Ca-EDTA provided some protective effect against the toxicity of cadmium. In this paper the authors attempt to clarify whether the drug, Ca-EDTA, could accelerate the urinary excretion of cadmium. The first experiment (A): 6 rabbits were injected subcutaneously with 3.37 mg of CdCl₂ every other day for 12 days. Three of the animals were given subcutaneously, one hour after the injection of CdCl₂, 141 mg of Ca-EDTA in 10 ml of 5% glucose solution. The remaining animals were set aside as controls and received only glucose treatment. Laboratory examinations were done on blood; erythrocyte and leucocyte count, hemoglobin content and serum protein content, and on urine; coproporphiline- and urobilinogentest. Cadmium content in urine as well as in organ tissues were measured polarographically. The second experiment (B): 10 rabbits were injected with 6.74 mg of CdCl₂ a day for three days and then with the same dose every other day for 14 days. After the last injection the animals were divided into two groups of 5 rabbits each. The animal of one group was administered 268.68 mg of Ca-EDTA in the same way as in (A) for 5 days. The other group served as controls and received only glucose treatment. The items examined in this experiment were, including those in (A), hematocrit value, blood specific gravity, and reti culocyte count. The third experiment (C): 6 rabbits were injected with radioactive cadmium in 1 ml of 0.34%-Cd^*(NO₃)₂, and one hour after the injection 3 of the animals were given 500 mg of Ca-EDTA and the remaining animals served as controls and received no treatment. The cadmium in 24 hour urine specimens was measured by the use of a scintillation counter. In this experiment cadmium content of every fraction of serum protein was determined by paperelectrophoresis. The results obtained were the followings: In the experiment (A): 1) Cadmium could not be detectable in the urine during the whole experimental period, but it appeard in a trial in which Ca-EDTA was given intravenously at the end of the experiment. 2) Cadmium content in liver and in kidney was slighter in a group administered with Ca-EDTA than in the organ tissue of the controls. 3) There were no other marked findings between the both groups. In the experiment (B): 1) Cadmium produced anaemia, such as a decrease of erythrocytes, hemoglobin content and hematcrit value. Ca-EDTA could not arrest these symptoms. 2) Ca-EDTA accelerated to some extent the urinary excretion of cadmium. 3) Cadmium content of the organ tissues showed no significant difference between the two groups. In the experiment (C): 1) Cadmium content in the urine sample was much larger in the animals administered with Ca-EDTA than that of the controls. 2) Cadmium content in the serum was diminished by Ca-EDTA. 3) The authors could not recognize a marked difference of cadmium content in every fraction of the serum protein.

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According to the method designated by ZOSEN KOGYO KAI (The Shipbuilding Association in Japan) to compute the expense incurred by diseases of workers, studies were made on the expense caused by worker's deseases in a shipyard which has approximately 11, 000 employees for the period from 1954 to 1956. This expense included the actual expenditure for medical care, loss on the part of the management incurred due to the absense of individual workers and other miscellaneous expenses and losses. The yearly total expense showed a gradual decrease but the expense during the summer and the winter time was larger than those in the other seasons due to the higher incidence of digestive diseases in the summer and the respiratory diseases during the winter time. Tuberculosis alone caused the expense of \1, 000, 000 monthly occupying 30-50% of the total expence. Due to the effective control, the expense incurred by tuberculosis showed a gradual decrease and the total expense for the third year was cut down by \46, 000, 000. The diseases of the digestive organs caused the total expense of two to five million yen monthly occupying approximately 15% of the total expense, and control of these diseases is considered to be very important. The diseases of the respiratory organs usually caused the expense of \1, 000, 000∼\2, 500, 000 monthly during the winter time, but an epidemic of influenza caused a three to five times rise in the expense with a monthly expense of \5, 000, 009∼\8, 800, 000. Popular and more frequent causes of sick leave such as headache, fever, stomachache and diarrhea incurred approximately \1, 000, 000 monthly.

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In order to evaluate the pathological conditions of leucocyte, it is necessary to find not only the changes of leucocyte count but also the functional conditions of leucocyte. Though there is not a satisfactory method to determine the functional activity of leucocyte, the phagocytic activity test seems to be one of the suitable methods. Many methods to determine the phagocytic activity of leucocyte have been proposed hitherto, but they are not satisfactory enough in the following respects : the facility to prepare the homogenous particle suspension, the high reproducibility of results, and the facility to observe the phagocytized particles. P-33 carbon black (Vundabilt, U.S.A.) was selected to satisfy these conditions. 150 mg of this carbon black were ground with 10 ml of 0.1% aqueous solution of gum arabic and one droplet of pure ethyl alcohol in a mortar, and centrifuged at 3000 r.p.m. for five minutes. The supernatant was recentrifuged in the same conditions. 0.1 ml of the suspension thus prepared, kept at 37°C, was added to 0.5 ml of anticoagulated blood kept in a waterbath at 37°C and incubated for 20 minutes, being shaken for 10 seconds every five minutes. After the incubation, smears were made and stained by Field's methods. The phagocytic activity can be expressed in two ways, i.e. percentage of phagocytosing neutrophils and mean number of phagocytized particles per one neutrophil. The former was almost constant for the incubation time of 10 to 60 minutes, whereas the latter increased considerably when incubated for a long time with the suspension of high concentration. Therefore, combined with technical covenience, it seemed better to determine the percentage of phagocytosing neutrophils to know the phagocytic capacity of the whole neutrophils.

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During these four years the authors have examined the prophylactic chemotherapy by INHG, on 128 patients who are thought as recovered from pulmonary tuberculosis, and on 24 patient under surveillance suspected of silicotuberculosis, at Hosokura Mine. The following results have been obtained. 1. In the X-ray observation 8.7 per cent of of 128 patients showed some improvement, no change for 89.0 per cent, and aggravation for 2.3 per cent. 2. The improvement rate was highest in the nodular type (28.6%), and secondary infiltrated caseous type (25.0%) fibrocaseous type (7.7%) followed in the order of improvement. 3. As to the term of improvement, 64.0 per cent of improvement cases were observed within 12 months and 27.0 per cent in further 6 months. 4. It could be recognized that some effect as regards the erythrocyte sedimentation rate, it's improvement rate was 22.7 per cent and it's aggravation rate was 5.5 per cent. 5. There was no significant effect in other physical examination results: body weight, vital capacity and tubecle bacilli in the sputum. 6. During the prophylactic chemotherapy of INHG, harmful subjective symptoms such as anorexia or constipation were observed in 11.0 per cent of the cases. But those complaints were so slight that no case had to discontinue the use of INHG. 7. Owing to this prophylactic chemotherapy, the recrudescent cases of pulmonary tuberculosis have diminished year by year since it's beginning, 1955. 8. The recrudescent cases of pulmonary tuberculosis for three years before and after the start of this examination decreased from 17 to 5. 9. On 24 patients under surveillance suspected of silicotuberculosis, in spite of long term prophylactic chemotherapy of INHG (over two years), there was no case of improvement but three cases of aggravation. The aggravation rate was 12.5 per cent and was considerably high compared with that of pulmonary tuberculosis, but was diminished to one third compared with the same group before three years and the degree of the aggravation also became so slight that it could be conjectured that some effect of this prophylactic chemotherapy on this group. 10. In other results by physical examinations, especially the decrease of vital capacity was distinguishied; 42.0 per cent of the cases were found as such. In view of the observation above described, the prophylactic chemotherapy of INHG showed some usefulness in the health administration of the persons under surveillance suspected of pulmonary tuberculosis and silicotuberculosis. On account of this usefulness, the prophylactic chemotherapy should be recommended more and more for the administration of those patients rather than limiting of labour conditions or mere follow-up observation. However, such conculsion on silicotuberculosis should be modestly accepted, because the term observed is not long enough and the number of patients examined is neither satisfactory.

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In order to investigate the shielding effect for X-ray irradiation, the author studied the influence of X-ray irradiation on phogocytic activity of neutrophils, red and white blood cell counts, and body weight. Twenty male rabbits were divided in the following four groups, i.e. A: control, B: whole body irradiation, C: upper half body irradiation ; D: limb irradiation. Dosage of irradiation of B, C, and D groups was 100 roentgens (4.5r/min: 25 minutes) each. Body shielding was prepared by a lead plate (1.5mm). After irradiation the animals were placed under observation for 5 weeks. Blood cell counts, body weight and phagocytic properties of neutrophils by observing the phagocytosis of carbon black were checked each week. The following results were obtained. (1) There were no appreciable changes of body weight by the irradiation. (2) Changes of red blood cell count was not observed. (3) In the group of whole body irradiation, the white blood cell count decreased one week after the irradiation and recovered to the initial count five week after. In the groups of partial irradiation, there was no changes of leucocyte count. (4) The percentage of phagocytosing neutrophils decreased in the irradiation groups and the decrease was more marked in the groups B and C than the group D. (5) Although the percentage of phagocytosing neutrophils showed a small individual difference, it was more susceptibly to irradiation than red and white blood cell counts.

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Characteristics of four methods of dust sampling which are now generally used to collect dusts in the atmosphere, i.e. those with pot collection, gummed paper, filter paper and electric precipitator, were compared. Radioactive fall-out and atmospheric pollutants were used as dust specimens. The efficiency of dust sampling of electric precipitator was better than that of filter paper when the amount in weight of dust collected was to be expressed, but vice versa when the efficiency was to be expressed in radioadtivity per unit air volume and per unit weight of dust. On the other hand, the sampling method with pot collection or gummed paper was considered inadequate for determining a concentration of atmospheric pollutants and only available to estimate a distribution or a trend of variation of atmospheric pollutants. And, it was found that the kinds of dust collected differed from each other when different sampling methods were used.

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