Change of flicker values according to seasons was studied on sixty healthy men, 18 to 38 years of age working in three 8-hour shifts under hot environment. Thermal conditions of the environment of the workshop were: in summer, air temperatures 28 to 40°C., relative humidities 80 to 85%, wind velocity 0 and in winter, 28 to 30°C, 75 to 80%, and 0, respectively. Followings are the summary of the results. 1) In the morning shift, ficker values before work are lower than those after work, in winter; on the contrary, in summer, such difference was not significant. In the night shift, values after work were lower than those before work in both summer and winter, especially in summer. 2) In each shift, the flicker values both before and after work were lower in summer than in winter. 3) Sleeping hours of these workers were shorter in summer than in winter. Therefore, the flicker value may be affected by the change of sleeping hours, temperature, and others.

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A group of 14 male medical students, having nearly the same daily life, was the subjects, and the effects of a mixture of potassium and magnesium aspartates were observed on the reaction time to light, the flicker value and the threshold of patellar reflex. Of the subjects, 9 received 40 ml in 10% solution of the mixture per day and the rest 5 were used as the controls, receiving the placebo. The main results obtained were: 1. Reaction time to light indicates no great difference between the two sets of subjects, though the administered showed somewhat more reliability in the reponse, i.e. the values observed were less scattered. 2. Flicker value was decisively enhanced from day to day in the administered, while all the controls remained unchanged. 3. Patellar reflex showed, in the administered, slow and later more faster lowerings in the threshold which settled somewhere around on the 3rd day; on the other hand, the controls registered increased threshold with the lapse of days. To sum up, the mixture looks to be effective for the recovery from fatigue, especially the nervous fatigue. The use of this may be recommended for the prevention of the accumulated fatigue.

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The principal component of Dieldrin is the endo-isomer of 1, 2, 3, 4, 10, 10-hexachloro-6, 7-epoxy-1, 4, 4a, 5, 6, 7, 8, 8a-octahydro-1, 4, 5, 8 dimethano-naphthalene, commonly abbreviated to HEOD. This chemical has been widely used all over the world as an insecticide in agriculture and public health and, in Japan, it was approved as an insecticide for environmental sanitation by the Ministry of Health and Welfare in 1956. Recently, Dieldrin has been newly developed in the field of mothproofing of wool (M. Lipson, ). Mothproofing with Dieldrin is very inexpensive as well as being remarkably effective, even at a low concentration. Although Dieldrin is considered to be almost ideal as a mothproofer, there are few reports on its toxicity as a mothproofing agent. This problem must be solved before discussing any hazard in its practical usage such as could be caused by dermal absorption from underwear, babies' sucking a part of their clothing etc. This is the basis and object of these experiments. Part I. Acute and Chronic Toxicity to Albino Rats. 1. Acnte oral toxicity of technical dieldrin (HEOD 85%) to albino rats was 39.5 mg/kg, and that of recrystallised dieldrin used in mothproofing (HEOD 96%) was 66 mg/kg which is about 50% lower than the former. 2. When rats were reared with woollen yarn impregnated witd 96% HEOD at 0.1% and 0.2% for 80 days, there was no change to the increase in body weight nor any increase in liver weight. At 0.5% and 1%, inhibition of growth was observed and at 3% and 5% rats were killed in a few days. 3. In the experiment in which an acetone solution containing 96% HEOD was applied to the skin of rats every day for 49 days, the inhibition of body weight increase was observed in the 5 and 10 mg/kg groups and the ratio of liver weight to body weight increased in the 10 mg/kg group. 4. The liver weight also increased in the orally administered group. 5. When the function of the liver is deducted from the increase of coproporphyrin in the urine, strong positive reaction increased in groups reared in knitting yarn treated at 1% (refined dieldrin) and over, and in the dermal application group and oral application groups at 5 mg/kg/day and above. With Mitin, all rats showed strong positive reaction from consuming 0.1% solution (about 100 mg/kg), and even at 0.01%, 40% of them showed strong positive reaction. 6. In case of liver hypertrophy, fatty degeneration was observed in histopathological findings. With acute intoxication and death, degeneration of liver cells (swelling and vacuolation) and karyolysis were observed and intense fatty degeneration was proven by Sudan III staining. On the kidney, congestion, karyolosis and swelling of the epithelial cells of the nephritic ducts were observed. 7. The main symptoms of intoxication of rats were excitation, tremor, clonic and tonic convulsions 8. The results of chemical analyses of faeces by the phenylazide method disclosed that dieldrin applied on the skin was partially eliminated into the digestive tract. 9. From the result of the chronic intoxication experiment of 49-92 days duration, it is estimated that the safety limit (threshold limit) for rats will be the absorption of less than 1 mg/kg of refined dieldrin. When the experiment is extended over a long period of time or young rats are involved, it is safer to lower this limit. Part II. Estimation of Absorption from Dieldrin-Impregnated Woollen Yarn Worn by Man and Extraction by Saliva. 1. Averaging 13 mg., maximum 21 mg. of dieldrin was lost when 4 men continually wore dieldrin impregnated woollen shirts (96% HEOD at 0.1%) for 60 days consecutively. If this amount of dieldrin were all absorbed and, additionally at the same rate from similarly treated trousers, the amount of dieldrin absorbed through the skin is estimated to average 0.008 mg/kg/day with a maximum of 0.0128 mg/kg/day. 2. [the rest omitted]

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