In the embryonic personality of the child, as well as in the undeveloped or narrowed individuality of the adult, the sense of the strange, of the unknown, and of the mysterious, is apt to arouse the fear instinct. In fact, the unfamiliar arouses the fear instinct even in the more highly organized mind. “Any new uncertainty,” says Bain, “is especially the cause of terror. Such are the terrors caused by epidemics, the apprehensions from an unexperienced illness, the feeling of a recruit under fire. The mental system in infancy is highly susceptible, not merely to pain, but to shocks and surprises. Any great excitement has a perturbing effect allied to fear. After the child has contracted a familiarity with the persons and things around it, it manifests unequivocal fear on the occurrence of anything strange. The grasp of an unknown person often gives a fright. This early experience resembles the manifestations habitual to the inferior animals.” In another place Bain rightly says, “Our position in the world contains the sources of fear. The vast powers of nature dispose of our lives and happiness with irresistible might and awful aspect. Ages had elapsed ere the knowledge of law and uniformity prevailing among those powers was arrived at by the human intellect. The profound ignorance of the primitive man was the soil wherein his early conceptions and theories sprang up; and the fear inseparable from ignorance gave them their character. The essence of susperstition is expressed by the definition of fear.” Compayré, in speaking of the fear of the child, says, “In his limited experience of evil, by a natural generalization, he suspects danger everywhere like a sick person whose aching body dreads in advance every motion and every contact. He feels that there is a danger everywhere, behind the things that he cannot understand, because they do not fit in with his experience. “The observations collected by Romanes in his interesting studies on the intelligence of animals throw much light on this question; they prove that dogs, for instance, do not fear this or that, except as they are ignorant of the cause. A dog was very much terrified one day when he heard a rumbling like thunder produced by throwing apples on the floor of the garret; he seemed to understand the cause of the noise as soon as he was taken to the garret, and became as quiet and happy as ever. “Another dog had a habit of playing with dry bones. One day Romanes attached a fine thread which could hardly be seen, to one of the bones, and while the dog was playing with it, drew it slowly towards him; the dog recoiled in terror from the bone, which seemed to be moving of its own accord. So skittish horses show fright as long as the cause of the noise that frightens them remains unknown and invisible to them.