Page:Popular Science Monthly Volume 17.djvu/168

156 objects. There is also a sensibility belonging to the muscles. When we make a motion—that of closing the hand, for example—we are not only aware of the effort we make to move the fingers and shut up the hand, but we also know that the movement is executed. Everything takes place as if the muscles were sensible, and each of the muscular contractions actually provokes a sensation. We should also distinguish between tactual and muscular sensibility and the sensibility to pain. When the skin is burned, or cut, or torn, the violent shock suffered by the nerves gives rise to a particular sensation, of which we have all had more or less experience, and which is called pain. The word is so clear and the thing so common that no other definition than the word itself is needed.

Some extremely curious observations may be made with patients who are wholly anæsthetic. We may prick them, pinch them, burn them, without their feeling the slightest pain. They do not perceive the contact of the objects that wound them. An experiment which always creates astonishment in persons who are not acquainted with medical practice is, to bandage the eyes of a patient, and scratch along her arm from place to place with a fine needle without her receiving the least intimation from her senses that she is wounded.

Anæsthesia is sometimes general and equally marked on the right and left sides, sometimes limited to a particular region of the body, as the forehead, the chest, or the forearm. Partial anæsthesia may occur even with patients who are only a little hysterical. If we seek to measure the sensibility of the different regions by pricking the skin lightly with a pin, we will often find a small zone of skin that is insensible. The Inquisitors of the sixteenth century had no other way of proceeding than this when they sought for the claw of the devil, only that, instead of touching the skin with pins, they made the executioner stick skewers of iron into all parts of the body. If the accused did not jump with pain at every implantation of the iron, they immediately declared that the devil had put his grip on her. The stigma of Satan was one of the most certain evidences of witchcraft. According to the most precise tokens of the exorcists, the devil's mark had the shape of a hare's paw.

Hysteric anæsthesia is often seated on only one side of the body; the affection in this form is called hemianæsthesia. The insensibility is so exactly limited to one side, that it is enough to go two or three millimetres to the right or left of the middle line of the body to establish the fact of the presence of sensibility or of its absence.

Although many researches have been made to discover the causes of this derangement of the nervous system, no satisfactory solution of the question has been reached yet. It seems to be proved that no material organic injury is connected with hysteria. The nerves of the affected side have the same appearance as the nerves of the healthy side; the marrow and the brains show no swelling, no hæmorrhage.