flicker値(FF)の生理学的意味を明らかにするにはチラツキの融合が,どの部位でおこるかを知ることである。Sherrington, Hecht, Granit以来,融合部位は網膜だと信ぜられてきたが,Walkerや小木の電気生理学的実験によって,視覚系に誘発される電位変動は,網膜でも融合するが,視覚皮質野では,その約1/2の低頻度で融合をおこすことが明らかにされ,また感覚的な融合頻度は,新皮質の興奮性を示す脳波のpatternとほぼ平行して変化することが,Gellhornや筆者によって確かめられた。また緊張や注意の集中によってFFが高進するのは,視覚中枢における生理的融合頻度の上昇とともに,視覚連合皮質の自発的興奮により,時間識別力が増大するためであって,おそらく中枢で生理的融合がおこる前に,これを感覚的に融合と判断する機能が,FFの基礎であると考えられる。 要するにFFは,視覚系をふくむ知覚連合皮質の興奮性の一つの表現であって,もし網膜の興奮性がほぼ一定に保たれ,またチラツキの出現点の判別に大きな誤差がなければ,FFは知覚皮質領域の興奮水準,あるいは意識の機能水準を示す生理学的指標とみることができ,また労働生理学や精神生理学の重要な研究手段として利用することができると考える。 FFは,疲労時に測定しても低下しないことがある。もし作業終了時のような,興奮が一時的に高まる時期に測定するとか,あるいはtestが被検者に興奮刺激を与えるようなことがあれば,FFの低下は陰蔽されて測定値に現われぬことも当然である。FFの測定が他の生理学的測定と最も異なる点は,testが被検者の意識状態を刺激し,それがFFを変化させること,つまり測定が不確定だということである。測定の物理的条件を一定にするだけではこの不確定性は解決されない。ここにflicker testの難かしさと意味が存在することを指摘し,測定の具体的な進め方について筆者の見解を述べた。

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Significance of biochemical testing method for evaluating the grade of fatigue and its possibilities to the practical application were discussed in the author's opinion. Brief summary of this discussion is as follows. It may be very important that the definition of fatigue is given clearly at first, however it seems to be difficult to lay down closely. We can only understand the fatigue ambiguously as a conception abstracted from subjective feelings, objective changes of various functions and efficiency of work which have accompanied a certain work load. This means that there is no absolute measure of fatigue, so that we can not properly estimate fatigue itself, no matter what kind of testing method we may use. It must be, therefore, taken into consideration that the result of the biochemical examination of which physiological mechanism is not clear cannot be serviceable for evaluating the physiological condition of fatigued subject. Although a considerable amount of attempts to seek after omnipotent method for fatigue test have been done in the biochemical field, it is not thought that these efforts will prove fruitful. Preferably, ordinary biochemical examinations of which physiological mechanism have been definite ought to be applied for estimating the physiological or biochemical processes during fatigued state. Biochemical examinations which are performed by using blood, urine or saliva as the test material have great merit to the effect that chemical substances in the body can be estimated without induction of any personal subjectivity. Nevertheless, biochemical examination dose not seem to be welcome on the actual spot. The reason is maybe that because the technical operations of sampling and testing are somewhat complicated for on-the-spot survey. If we make efforts to simplify the operation method and to have mind not to estimate fatigue itself, but to study the physiological and biochemical mechanism of fatigued state, the biochemical examination would be more useful for the study on fatigue and its way of practical applications would be more developed than before.

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Premedical and chronic changes in several organs and the preventive measures of them are discussed briefly at the level of causative agents. 1) It has been experienced that too much intake of animal food is accompanied by a high incidence of diabetes mellitus. This disease is prevalent among persons of manager class or of wealth but seldom among ordinary people in Japan. Moderate intake of animal food appears to have to be advised. 2) Old people living at the intake level of 1500 Cal. and 40g. total protein, of which less than 10g. is from animal source, are many in Japan. They are characterized by marked body weight reduction. The situation is linked with the intake level among young people. Calory and animal protein have to be encouraged to increase for these people. 3) There are many kinds of highly salted (10∼30%) food in Japan. They are routinely consumed with insufficient mastication. Highly salted food causes damage in stomach membrane through many folds of normal osmotic pressure. Health education for the Japanese appears to be needed to advise them to mince or desalt before eating or to masticate enough to desalt in the mouth. 4) Repeated cold stimuli, which are very often to be seen in everyday life of the Japanese, have been reported to be linked with hypertension and cerebral apoplexy, that are very prevalent in Japan. Cold stimuli in the living conditions have to be sought and evaluated individually from the viewpoint of preventing the diseases. 5) Energy consumption for going up the stairs is very large. Repeated tachycardia accompanies enlargement of the heart, when it becomes weakened. Tachycardia and tachypnea in ordinary life are good measures for screening weakend heart and for preventing its aggravation by avoiding the symptoms. 6) Health hazards and poisoning from environmental conditions should be avoided by the estimation and by the improvement of the environment before any sign of disease can be recognized. The present measures adopted in Japan are not necessarily suitable.

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In normal excitation of the muscle fibres, the action potential arising from the neuromuscular junction (end-plate) propagates along the surface of the muscle fibre. When the depolarization induces a marked increase of the permeability in the muscle membrane, the action potential is manifested reflecting a rapid entry of sodium into the cell followed by an outflow of potassium (Hodgkin, 1951; Hodgkin & Huxley, 1952). It, however, is stated by many authors that there is no direct essential links between the action potential and the initiation of the contractile mechanism, but unknown physiological intermediate steps between them (Excitation-Contraction Coupling. Sandow, 1952). Hill & Howarth (1957), Hodgkin & Horowicz (1960) suggested that a depolarization, somewhat less than required to cause contraction, can release some chemical reactions that has been physiologically produced by excitation. In this paper, the author reviewed results of the study on the E-C coupling which recently has been reported.

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During endurable muscular work, the maximal strength was found to be modified by several factors like proprioceptive activity, sound stimulus, drugs as well as hypnosis. The subject contracted the arm flexor isometrically against the horizontal bar attached with a straingauge recorder once two seconds with the maximal effort up to exhaustion. The electromyograms were recorded from the brachial biceps, brachial triceps and flexor carpi radialis. It was found that the discharge of motor units to the flexor muscles was increased at a stage when the maximal strength was decreased by twenty percent of the initial level of the strength. In the next experiment, the subject contracted the arm flexor on the arm ergometer with a load of 1/3 of the maximal strength once a second up to exhaustion. It was found that electromyograms from the flexor gradually increased in voltage and frequency on later stage of the work. It was supposed that the psychological limit was elevated due to an increased activity of proprioception on the arm after the fatigue of muscle fibers. In later stage of the endurable work with the straingauge tensiometer, the subject was given a sound of "shout" of starting gun or a sound of "shout" by himself. It was found that the maximal strength recovered up to the initial level of the strength and sometimes over the initial level of the strength together with an increase of nerve discharge to the arm flexors. It was supposed that the psychological limit was elevated due to "disinhibition" on the central nervous system with the sound stimulus. It was worthy to note that the elevated level of the maximal strength after administration of amphetamine sulphate was almost the same as with "shout". Hypnosis, however, was most effective for improvement of the expression of the maximal strength. It was supposed that hypnosis induced "disinhibition" on the brain. Here were shown the factors which modified the onset of muscular fatigue and the mechanism was discussed from view point of psychological limit and proprioceptive activity.

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1. We discussed methodologically the practical procedure to estimate and analyse qualitatively the physical load by heavy muscular labor. 2. From the view-point of medical practice in industrial health, we originated several new methods which were probably useful for analysis of the physical load by muscular labor. These methods were as follows: a) the graph showing work time distribution regarding the heaviness of muscular labor b) the original method to indicate the physiological characteristic of hot work environment c) the partitive estimate of heat balance at heavy work in hot environment d) Q-T index, an integrating value of heat storage. 3. Our labor investigations with several inportant jobs in iron works were carried out in suchs steps as follows: a) survey of working condition b) physiological study of physical effect by muscular labor c) diagnosis of "fatigue type" d) planning for improvement of working condition. 4. Two cases of our investigations on muscular labor were briefly stated. The one was a fatigue study on steel plate making job, and the another was a comparative observation on steel plate making and crane operating jobs with special reference to their qualitative difference.

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