In health, under most favorable circumstances, shock is injurious to the mind and body. The sudden announcement of the death of a relative or the loss of fortune has been known to cause death in persons afflicted with heart disease or liable to apoplexy or other dangerous conditions. Great fright has often unbalanced the mind, and violent exertions may produce serious conditions.

Whatever may become a source of danger at any time may be made a source of danger by the hypnotist. It must not be supposed that because a person is "only hypnotized," he runs no risk of danger. The mind and body are not changed in any way and both are susceptible to injury, for there is no charm about hypnosis.

It may be interesting to spectators to make a subject laugh and express the greatest of joy and then suddenly change his emotions to those of great and violent grief. But it is dangerous to do this if the subject has a weak heart or if he is liable to apoplexy. To him the shock is just as real and impressive as it would be were the sudden change from joy to grief an actual occurrence of real life.

Catalepsy should not be suddenly induced in a subject whose heart is weak. The shock of realizing that he cannot move his muscles might possibly prove disastrous. If it is at all desirable to produce catalepsy in such subjects, it is best to prepare the mind for it by such words as: "Soon you will realize that you cannot move a muscle of your body. The sensation will be a pleasant one and it will not harm you, for I will give you the power to move again in a short time."