Page 105.
Several kinds of snakes inflate themselves when irritated. The puff-adder (Clotho arietans) is remarkable in this respect; but, I believe, after carefully watching these animals, that they do not act thus for the sake of increasing their apparent bulk, but simply for inhaling a large supply of air, so as to produce their surprisingly loud, harsh, and prolonged hissing sound.
ERECTION OF THE EARS.
Page 111.
The ears through their movements are highly expressive in many animals; but in some, such as man, the higher apes, and many ruminants, they fail in this respect. A slight difference in position serves to express in the plainest manner a different state of mind, as we may daily see in the dog; but we are here concerned only with the ears being drawn closely backward and pressed to the head. A savage frame of mind is thus shown, but only in the case of those animals which fight with their teeth; and the care which they take to prevent their ears being seized by their antagonists accounts for this position. Consequently, through habit and association, whenever they feel slightly savage, or pretend in their play to be savage, their ears are drawn back. That this is the true explanation may be inferred from the relation which exists in very many animals between their manner of fighting and the retraction of their ears.
All the Carnivora fight with their canine teeth, and all, as far as I have observed, draw their ears back when feeling savage.
A STARTLED HORSE.
Expressions of the Emotions,
page 130.
The actions of a horse when much startled are highly expressive. One day my horse was much frightened at a drilling-machine, covered by a tarpaulin, and lying on an open field. He raised his head so high that his neck became almost perpendicular; and this he did from habit, for the machine lay on a slope below, and could not have been seen with more distinctness through the raising of the head; nor, if any sound had proceeded from it, could the sound have been more distinctly heard. His eyes and ears were directed intently forward; and I could feel through the saddle the palpitations of his heart. With red, dilated nostrils he snorted violently, and, whirling round, would have dashed off at full speed, had I not prevented him. The distention of the nostrils is not for the sake of scenting the source of danger, for, when a horse smells carefully at any object and is not alarmed, he does not dilate his nostrils. Owing to the presence of a valve in the throat, a horse when panting does not breathe through his open mouth, but through his nostrils; and these consequently have become endowed with great powers of expansion. This expansion of the nostrils, as well as the snorting, and the palpitations of the heart, are actions which have become firmly associated during a long series of generations with the emotion of terror; for terror has habitually led the horse to the most violent exertion in dashing away at full speed from the cause of danger.