370 POPULAR SCIENCE MONTHLY. 



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 fre- 

 quently 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 in- 

 stances, 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 im- 

 portant 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 

 Zoological Gardens. This dangerous brute, which had injured sev- 

 eral 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 



