Sir W. Scott’s famous Scotch greyhound, Maida, had this habit, and it is common with terriers. I have also seen it in a Spitz and in a sheep-dog. Mr. Riviere, who has particularly attended to this expression, informs me that it is rarely displayed in a perfect manner, but is quite common in a lesser degree. The upper lip during the act of grinning is retracted, as in snarling, so that the canines are exposed, and the ears are drawn backwards; but the general appearance of the animal clearly shows that anger is not felt. Sir C. Bell[503] remarks “Dogs, in their expression of fondness, have a slight eversion of the lips, and grin and sniff amidst their gambols, in a way that resembles laughter.” Some persons speak of the grin as a smile, but if it had been really a smile, we should see a similar, though more pronounced, movement of the lips and ears, when dogs utter their bark of joy; but this is not the case, although a bark of joy often follows a grin. On the other hand, dogs, when playing with their comrades or masters, almost always pretend to bite each other; and they then retract, though not energetically, their lips and ears. Hence I suspect that there is a tendency in some dogs, whenever they feel lively pleasure combined with affection, to act through habit and association on the same muscles, as in playfully biting each other, or their masters’ hands. I have described, in the second chapter, the gait and appearance of a dog when cheerful, and the marked antithesis presented by the same animal when dejected and disappointed, with his head, ears, body, tail, and chops drooping, and eyes dull. Under the expectation of any great pleasure, dogs bound and jump about in an extravagant manner, and bark for joy. The tendency to bark under this state of mind is inherited, or runs in the breed: greyhounds rarely bark, whilst the Spitz-dog barks so incessantly on starting for a walk with his master that he becomes a nuisance. An agony of pain is expressed by dogs in nearly the same way as by many other animals, namely, by howling writhing, and contortions of the whole body. Attention is shown by the head being raised, with the ears erected, and eyes intently directed towards the object or quarter under observation. If it be a sound and the source is not known, the head is often turned obliquely from side to side in a most significant manner, apparently in order to judge with more exactness from what point the sound proceeds. But I have seen a dog greatly surprised at a new noise, turning, his head to one side through habit, though he clearly perceived the source of the noise. Dogs, as formerly remarked, when their attention is in any way aroused, whilst watching some object, or attending to some sound, often lift up one paw (fig. 4) and keep it doubled up, as if to make a slow and stealthy approach.