FATAL CURRENT.
The amount of current which will produce a fatal effect varies with the character of the current and with the points of contact. Currents passing through the head or those which affect the pneumogastric nerves are much more dangerous than others of the same character and equal strength passing through one extremity, for example.
The same current will, of course, also produce different effects, according to the facility of its conduction into and through the body, and this depends again on the completeness of the contact and whether the body or the portion thereof concerned enters directly into the circuit or only forms, as it were, a partial conductor and diverts a certain portion only of the current to itself. Again, the condition of the epidermis, whether dry or wet, and the position of the person in relation to good conductors, metallic or otherwise, has much effect.
If the skin and clothes be wet, the resistance to the current is lessened and it passes more readily into the body. In the same way, if a person stands in close relation to a good conductor and places his hand on one wire of a high-tension electric circuit, he will receive a much more severe shock than if not connected with such conductor. Thus a person standing in a pool of water (water is a good conductor), and more strongly if standing on the metallic rail of a railway track, and touching one wire of an electric circuit with one hand, receives a much stronger shock than if he were standing on dry land, or if his boots were rubber or he was otherwise insulated.
The accidents most frequent in practice are those in which the current has been partially diverted from its original course and the person has not entered fully into the circuit. In such cases it is not usually possible to estimate accurately or even approximately the amount of current which the person has received. No calculations can, therefore, be based on these accidents. Again, we find that a person may be seriously or even fatally injured by a current which another person seems to bear with impunity.
D’Arsonval in 1887, in France, advised 500 volts as the maximum for the continuous current and 60 volts as the maximum for the alternating current which might be employed without special permission.
Our only accurate knowledge in regard to fatal currents comes from the experience derived from electrocutions. From these it appears that an alternating current of 1,500 volts is deadly if it passes through the body for more than a few seconds and if the contact is perfect.
Death.—Death may ensue immediately as the result of an electric shock without any evident preliminary symptoms, or it may occur later, either as the direct result of the shock or as the consequence of the exhaustion produced by the burns and other injuries, or directly from the injuries themselves. If death does not occur immediately and if appropriate means of aid are at hand, the sufferer usually survives and the effect of the electric shock gradually passes away. The danger after this arises from the burns and other injuries, and almost all the deaths not immediate are the results of these.