Hunters in wild and strange lands have told us that often when they were lying concealed for the purpose of shooting the wild animals when they came within range, they have witnessed instances of the existence of this strange faculty in the wild beasts. Though they could not see the concealed hunters, nor smell them (as the wind was in the other direction) all of a sudden one or more of the animals (generally an old female) would start suddenly, and a shiver would be seen to pass over its body; then it would utter a low warning note, and away would fly the pack. Nearly every hunter has had the experience of watching his expected game, when all of a sudden it would start off with a nervous jerk, and without waiting to sniff the air, as is usual, would bolt precipitately from the scene. Moreover, many beasts of prey are known to sense the presence of their natural prey, even when the wind is in the other direction, and there is no sound or movement made by the crouching, fearstricken animal. Certain birds seem to sense the presence of particular worms upon which they feed, though the latter be buried several inches in the earth, or in the bark of trees. Savage man also has this faculty developed, as all travellers and explorers well know. They are as keen as a wild animal to sense the nearness of enemies, or, in some cases, the approach of man-eating beasts. This does not mean that that these savages are more highly developed than is civilized man--quite the reverse. This is the explanation: when man became more civilized, and made himself more secure from his wild-beast enemies, as well as from the sudden attacks of his human enemies, he began to use this sense less and less. Finally, in the course of many generations, it became almost atrophied from disuse, and ceased reporting to the brain, or other nerve centres. Or, if you prefer viewing it from another angle, it may be said that the nerve centres, and brain, began to pay less and less attention to the reports of this sense (trusting more to sight and hearing) until the consciousness failed to awaken to the reports. You know how your consciousness will finally refuse to be awakened by familiar sounds (such as the noise of machinery in the shop, or ordinary noises in the house), although the ears receive the sound-waves.