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pleading countenance, stretch out his arm to the punisher, if the ape was still being punished, try to hold one arm tight, and finally, with exasperated gestures, start hitting out at the big man!” It is in fact dangerous to punish an ape among a number of adult animals. Even a slight, complaining sound may bring the whole pack in an angry assault upon the offending man. It matters little what the cause of the outcry. Even a good-tempered and affectionate chimpanzee may become suddenly infected with the epidemic of rage that seizes the group, and attack one with whom it had been playing a few moments before. Mob psychology among chimpanzees is only a little more impulsive and unreasoning than it is among ignorant human beings.

The desire of a chimpanzee to be a member of a group is inordinately strong. If isolated, he is very unhappy. Some fall a prey to fears; others cry, scream, and rage violently until overcome by exhaustion. If a chimpanzee is confined alone in a cage surrounded by his comrades, it often happens, says Köhler, “that if it is only possible for them to get near the prisoner’s cage, one or other of the animals will rush to it and put his arms round him through the bars. But he has to howl and cry for this affection to be shown him; as soon as he is quiet, the rest of them do not worry.”

The highly social and sympathetic nature of chimpanzees often leads them to form strong attachments to their keeper. They are quick to sense the emotional attitudes of their human companions and to guide their conduct accordingly. They have their favorites among human beings, often for reasons which appear quite capricious, and they are equally capricious in exhibiting strong dislikes to individual animals as well as persons. They wish to feel that they enjoy the favor of their keeper, and they become very jealous of his attentions to other animals. The pain felt by chimpanzees