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v spinal cord and the brain, and may become an index or reflector of what is going on within that brain. Tails may of course be used in different ways; the cat waves its tail when it is angry, the dog when it is pleased. That is merely matter of habit; but in each case the motion is the result of some affection of the nervous system. Now the nervous system of birds is very sensitive, if we may judge by their restlessness, and by the extreme vigilance and rapidity of their sight and all their motions. And this in many birds, and especially in small ones, is apt to show itself in the tail, which is flickered horizontally, as in the Redstart, or jerked upwards, as in the Wren and Moorhen, or twitched several times in a minute, as in the Yellowhammer and Reed Bunting, the Wheatear and Whinchat, and others. The motion may mean either simple satisfaction, or sometimes distress and alarm. With most of the birds I have mentioned the former is the cause, though not, I think, invariably; but watch a Red-backed Shrike as you approach his nest or young, and you will see a good example of the effect of anger on a tail. He sits on the top of the hedge, swinging his tail from side to side, as well as up and down, with a motion quite peculiar to