An animal has a much greater gift of expression than a plant or a rock, and we feel that animals are much nearer to us. The dog by wagging his tail, by jumping about, by his every movement says, 'I love you',  and we care much more for him. We do not want the plant on the chair next to us, but if the dog sits on the chair it is all right. The cat has no words either, but all the same it speaks to us with its voice. In all parts of the world people have praised the nightingale because of its voice, its expression. There are many birds in the forests of which we never think because they have no voice. But the song-birds we all know, and we like to keep a parrot because it can speak.