Recently, there have been mary reports as to the erythrocyte δ-aminolevulinic acid dehydratase (ALA-D) activity of lead workers and lead administrated experimental animals. But, there have been only a few data that investigated the factors effecting the variation of ALA-D activity from the subjects not occupationally exposed to lead. This study was intended to know some factors influencing on the normal ALA-D activities of rats and humans. The ALA-D activity of male Wistar rats were determined in relation to age and the effect of blood drawing was examined. The ALA-D activity of inhabitants in rural and urban districts were also determined.
The results were as follows :
1) The ALA-D activity of intact rats showed 0.77±0.09μmoles PBG/h/ml RBC in those at 3 weeks of age, 0.11±0.02 in 9 weeks, 0.14±0.06 in 17 weeks, 0.15±0.07 in 27 weeks, and 0.19±0.02 in 58 weeks. The value of ALA-D activity of rats indicated remarkable decrease before 9 weeks of age, and then became stable up to 58 weeks, though with apparently slight increase. Those phenomena kept pace inversely with body weight of rats up to 250g.
2) Blood drawing gave a marked difference of ALA-D activity between young and adult rats. The ALA-D activity 24-48 hours after blood drawing was elevated considerably in young rats as compared with adult ones.
3) An excellent inverse correlation was found between erythrocyte ALA-D activity and peripheral blood findings of rats. The coefficient of correlation of ALA-D activity with Ht, Hb and RBC value was -0.91, -0.81 and -0.78, respectively.
4) The ALA-D activity in urban population were studied in three age groups (6 children, 146 youths and 20 the aged). There were no differences in ALA-D activity by age and sex.
5) The ALA-D activity in rural residents 47 years old and over were examined too. Significant statistical difference of ALA-D activity was observed between males and females (p<0.001).

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A follow-up study of 164 patients with vibration disease after their discharge from the hospital was performed to clarify the points in occupational rehabilitation. The subjects were 164 male patients who had used chain saws in the national forestry and hospitalized for 3 months or more. Questionnaires containing subjective symptoms, treatments in clinic, conditions of work, daily habits (smoking, drinking, exercise and skin rubbing with dry towel) prophylaxis were mailed to all the subjects, and all of them returned to us. The subjects were divided into two groups : A group included 73 cases with less than 3 months of hospitalization, and B group had 91 cases with 3 months and more of hospitalization. The period from the discharge to the time of filling questionnaires was 2 to 21 months.
Of seventeen items of subjective symptoms, the rates of pain of shoulders, headache, disturbance of sound sleep and tinnitus in B group were significantly higher than those in A group. The complaints due to the primary lesions of the joints and the muscles were higher than the others.
All the subjects had resumed their work on 29.5th day on an average after their discharge. Treatments as outpatients consisted of administration of drugs, physical therapy with cervical traction, hot pack on shoulders or arms, paraffine bath, etc.
Physical conditions in all the patients were indicated by three grades from self-evaluation with “good, ” “fair” and “poor.” The evaluation of “fair” and “poor” showed more than 80 per cent. It would show that the neurotic aspect of the patient with vibration disease is more prevalent in the present survey in the comparison with the data of our clinical experiences and our another survey.
In conclusion, as problems in the occupational rehabilitation there are two points : how to manage orthopedic complaints, and education of the patient concerning the disease.

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It is generally accepted that the load of mental work is estimated from the changes of physiological function during or after the work. Points to be considerated in this estimation were studied.
Subjects were 5 healthy male adults. As mental work the target aiming task was assigned. This task is thought to reveal the function of concentration maintenance and is assigned for one, three, or fifteen minutes.
Means of the task performance (L), deviations of performance (D), and the reliability of the task control (D/L) were determined respectively from the recorded curve. On the other hand, heart rates and blinking frequencies were observed polygraphically.
The results were as follows :
1) The mean of the task performance (L) decreased with the prolongation of the aiming duration.
2) The frequency of blinkings decreased significantly during the aiming task. However, the similar phase in frequency of the control condition appeared irregularly during the aiming task. Grouping of blinkings was frequently observed with the prolongation of aiming duration.
3) Immediately before the beginning of the task, heart rate increased rapidly on giving the subject instructions to prepare for the aiming. After the beginning of the aiming, heart rate decreased rapidly and reached to a lower level than that of the control condition. However, heart rate increased gradually with the prolongation of aiming duration and reached to the similar level as the control condition. Immediately after the end of the aiming task, heart rate increased rapidly, and the degree of this increment correlated with the duration of the aiming task. And more- over, the individual difference in this increment was found to be based on the individual autonomic balance.
4) The deviation of heart rate decreased in the early stage of the aiming period.
5) It was shown that the work-performance related to the autonomic balance.
From these results, it may be concluded that the individual characteristics of the physiological response have to be taken into consideration when the load of mental work is estimated from the change of the physiological functions.

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The adsorption of ammonia gas on eight kinds of zeolites was measured by the static method at 30°C and up to 70, 000ppm. The difference in the adsorption of ammonia gas on activated carbons and zeolites was examined through the results of amount adsorbed, adsorption isotherm, and rate of adsorption. The relations between the amounts of ammonia gas adsorbed on zeolites, rate of adsorption and their physical properties were discussed as to specific surface area, pore volume, and pH.
The results were as follows :
1) The amount of adsorbed on each zeolite was roughly the same and was approximately 40 times as much as that on the activated carbons (No. 2, No. 3, and No. 6) at lower equilibrium concentrations up to 1, 000ppm.
2) The adsorption isotherms of ammonia gas on the activated carbons and zeolites were found to follow Freundlich's equation and Langmuir's equation, respectively.
3) The rate of adsorption of the zeolites of which pore diameters were 3 Å and 4 Å was much slower than that of activated carbons, and their time of reaching adsorption equilibrium was about 40-70 min, but the rate of adsorption on the zeolites of which pore diameters were 9 Å, 13 Å were the same as that of the activated carbons.
4) Adsorption of ammonia gas on the zeolites seemed to be mainly physical as judged from the value of heat of adsorption.
5) It may be concluded that amounts of ammonia gas adsorbed on the zeolites was determined mainly by their pH's rather than their porous structure, whereas the rate of adsorption was determined by their porous structure such as specific surface area and pore volume.

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