Page:Popular Science Monthly Volume 53.djvu/386

370 been called forth by my stating in an article on Canine Morals and Manners (lately republished in Wild Traits in Tame Animals) that a dog's pupils dilate when he is angry. The evidence upon which I based this statement was gathered at the house of a friend who had a fox terrier which used to become furious when teased. It had a basket in the corner of the room to which it retired when offended. The light from the chandelier shone full upon its face, and I frequently observed that when the animal was especially angry the eye chambers reflected the light in the same way as do those of a human being when the pupils are dilated with atropine. Having no quarrel with the animal myself, I could approach him with safety when others were exciting his wrath, and found that on such occasions the pupils of his eyes were widely open. It so happened that about the same time Sir S. Wilkes had been making observations upon parrots, and found that the pupil contracted when the birds were under the influence of anger. On extending my observations to other animals, I found that cats and monkeys exhibited the same peculiarity as the dog when enraged and meditating mischief, but that in several instances, as soon as the creatures were provoked beyond endurance and flew at their persecutors, the pupils suddenly contracted. I offer the following conjecture as to the reason of this phenomenon: When an animal is angry and face to face with a foe, but has not made up its mind as to the most effective method of attack, it is important that the eyes should take in as much as possible of the enemy and his surroundings; but when the actual onslaught is made, the attention of the assailant is fully concentrated upon some particular point of his adversary's body.

One of the most remarkable instances of dilatation of the pupil during anger which I have observed was in a black panther at the Zoölogical Gardens. This dangerous brute, which had injured several people and was usually kept in the background away from the general public, sprang at the bars when the keeper touched him with a stick, and his yellow circular irises became narrowed to mere bands, so that the pupils were enormously dilated. This gave the eyes an expression of indescribable ferocity, for they reflected so much light from their interior as to appear as if red flames were glowing within.

There seems to be a good deal of doubt as to the reason why the eyes of animals shine in the dark. One often hears it stated that the eyes of certain beasts emit light on their own account as if they were phosphorescent. I have never been able to verify this statement, and am inclined to think that it is a mistake. In all cases where I have personally observed this shining of the eyes, the light has obviously been reflected. Our attention is usually drawn to the phenomenon