Not one of the above movements, so clearly expressive of affection, are of the least direct service to the animal.
They are explicable, as far as I can see, solely from being in complete opposition or antithesis to the attitude and movements which, from intelligible causes, are assumed when a dog intends to fight, and which consequently are expressive of anger.
This contrast in the attitudes and movements of these two carnivorous animals, under the same pleased and affectionate frame of mind, can be explained, as it appears to me, solely by their movements standing in complete antithesis to those which are naturally assumed, when these animals feel savage and are prepared either to fight or to seize their prey.
In these cases of the dog and cat, there is every reason to believe that the gestures both of hostility and affection are innate or inherited; for they are almost identically the same in the different races of the species, and in all the individuals of the same race, both young and old.
I request the reader to look at the four accompanying sketches, which have been given in order to recall vividly the appearance of a dog under these two states of mind.
It is, however, not a little difficult to represent affection in a dog, whilst caressing his master and wagging his tail, as the essence of (56) the expression lies in the continuous flexuous movements. When this animal is threatened by a dog, it arches its back in a surprising manner, erects its hair, opens its mouth and spits.
Had not the change been so instantaneous, I should have attributed it to his lowered spirits affecting, as in the case of man, the nervous system and circulation, and consequently the tone of his whole muscular frame; and this may have been in part the cause.
We will now consider how the principle of antithesis in expression has arisen.
I will here give one other instance of antithesis in expression.
I formerly possessed a large dog, who, like every other dog, was much pleased to go out walking.