Industrial Electricity
With the increased use of electricity for motive power and illumination instances of injury and even death have occurred, and probably will become more frequent. One of the most important safeguards of the body against the effects of electricity is its high degree of resistance, especially if the body surface be dry. Moisture of the body surface lessens the resistance and increases the liability to injurious effects.
The body is a bad conductor; it is said to be three million times less than mercury, and fifteen million times less than copper; the nerves conduct like metals. The danger of electric shocks depends upon the amount of current passing through the body, the kind of contact, and the insulation of the body at the time. Moisture of the body or clothes will increase the effects of the shock. Much depends upon the quality, duration, strength, and density of the current, and the direction in which it passes.
The continuous current is less severe than the interrupted, and the alternating is the most powerful in its effects. An alternating current of 300 volts has caused death, and one of 1500 volts would certainly prove fatal, whereas for the continuous current it would take 3000 volts to prove fatal.[13] Cases are recorded when with good contact even so low as 65 volts has proved fatal. The Board of Trade forbids the introduction into dwelling-houses of currents of more than 250 volts, unless for special purposes and with special permission.
As the current enters or leaves the body it may cause local injury. Tetanic muscular contractions with pain, and pain from stimulation of nerve endings in the skin with erythema may occur. Burns produced by electricity may be accompanied by much local destruction of tissue and slow healing.
There may be ascending neuritis from injury to nerves.
The shock may cause insensibility with pallor and stertorous breathing; the skin is moist, the eyes suffused, and the pupils dilated.
Death is due to (1) inhibition of the medulla oblongata, or (2) direct action on the heart muscle. According to the researches of Cunningham, currents which traverse the whole body transversely or longitudinally produce fibrillary contraction of the heart muscle. When the current passes through the brain, medulla, and upper cord it may cause death by respiratory paralysis. Those who have recovered from severe shock describe the sensation as peculiar rather than painful.
Post-mortem Appearances.—These include the local injury, if any, at the point or points of contact, some hyperæmia of the internal organs, œdema of the lungs, and fluidity of the blood. The general appearances are those of asphyxia. Kratter considers that external burns in association with subpericardial and subpleural ecchymoses, and especially subendocardial petechiæ, also the presence of congestion of the bronchi, strongly indicate death from electricity.
Minute hæmorrhages may occur in the meninges, and in the fourth and other ventricles. Changes have also been described in the cells of the central nervous system in experiments upon animals.
Treatment.—The current should be switched off at once; the patient should be removed from the conductor, the rescuer being protected with some insulating material, the attempt should not be made bare-handed.
Stimulation, warmth, and artificial respiration should be resorted to. After respiration has been re-established, friction should be applied to the body. The treatment should be persevered in for several hours. Signs of life may not be seen for two hours. Venesection may be desirable.