The bird dog knows of the presence of a game bird before he can see it. He scents its location at long range. He is trained to "stand" when he recognizes the scent. With one paw lifted, his nose and tail stretched out to their greatest reach, he points his master to the spot where the game is to be found. At the word of command he moves cautiously forward towards the bird, and when his master is ready another word causes the dog to "flush" the bird, or make it take wing. The hound upon the track of fox or deer has remarkable power, not only of following the exact track made by the pursued animal, even when some hours have elapsed since the game passed that way, but his scent is so keen that in many instances he is able to tell, when he comes upon such a track, which way the deer or fox was running. Sometimes the hound "takes the back track," but the best dogs are usually so positive in this sense that they make no mistakes as to which way the animal has traveled. It is common knowledge, but none the less marvelous, that an ordinary dog is usually able to follow his master by scent alone through the crowded streets of the city or across fields where a thousand fragrant flowers and grasses seem to arise on purpose to baffle him. This marvelous power is not confined to dogs. Many other animals possess it in a remarkable degree. The keenness of this sense in deer, antelopes, and other wild ruminants is so well known that hunters despair of ever approaching them except from the side which gives them the wind in their faces so that their own peculiar scent may be carried away from the extremely sensitive nostrils of their game. The hippopotamus has this sense highly developed and can discover his human enemy without getting sight of him or hearing his approach. The polar bear climbs upon an iceberg and sniffs afar the dead whale floating his way, although still miles toward the horizon. The camel in the desert is often saved from death by the keenness and accuracy of his olfactory organs, which tell him the direction he must take to fill his depleted reservoir with water. The North American Indian smells as keenly as he sees, for he can not only detect the presence of human beings by his nose alone, but also surely tell whether they are of his own or the suspected white race. In the Massachusetts Asylum for the Blind was a mute girl named Julia Brace, who knew her friends and acquaintances by the peculiar odors of their hands. Not being able to see them or converse with them, she was compelled to distinguish them by the sense of smell alone. So remarkable were her powers that she was regularly employed in assorting the clothes of the pupils as they came from the wash, that operation not being far-reaching enough to remove the signs which were known to her alone. The case of James Mitchell, who was deaf and blind from his birth, is remarkable, for he could detect the approach of a stranger in this way.