The monotony of a captive animal’s life is broken only by feeding, the sight and sounds of others in the same building or nearby, and by visitors. Many animals show their appreciation and pleasure when visitors approach, and some of the more intelligent animals, bears and monkeys and some birds, “show off” apparently to keep the visitors there. When there is nothing doing, some stand swaying their heads, like a weaving horse, or pacing the cage, inanely tagging at each turn the side of the cage with the head or other part of the body—often so persistently that a sore is produced. Nearly all animals are social and suffer from loneliness when kept by themselves. This is true even of the lowly forms. The keeper of the reptile house reported that a giant tortoise became despondent and refused to eat when his companion, a leopard tortoise, was taken from him, and that he braced up as soon as the leopard tortoise was returned. It is not necessary that the companion be of the same species, or even of the same family. A lion or a tiger may be satisfied with a little dog for a companion, and there was an African rhinoceros at the Philadelphia Garden that was very discontented and unhappy when alone and became perfectly satisfied when she was given a domestic goat as a cage-mate; and the huge rhinoceros stood for a good deal of butting and bullying from the goat without retaliating. A sympathetic keeper may do much to relieve the loneliness of the animals in his care. Nostalgia, or homesickness, has been felt by all men. Some have died of it. The tradition among writers is that it affects young people and those who have been living nearest to a state of nature. In this country the American Indian and the negro are affected more than the whites. Much was written of it after the Franco-Prussian War and the American Civil War. It is a real condition, capable in extreme cases of causing death and of so weakening the sufferer as to make him more susceptible to the invasion of other diseases. At the present day we hear less of it among civilized people than formerly, perhaps because the conception of home has been broadened by modern methods of intercommunication. The wild animal’s conception of home is narrow; he comes directly from it into an environment where he may see many other animals, but not one of his own kind. Predisposing causes of nostalgia are stronger with him than with the human. That home means a great deal to animals is shown by the migration of birds—the return of the carrier pigeon, and of the lost dog, and of the swallow, which returns every year to the same nesting place. All animals long for the things of nature—open air, earth, grass and water. They are thrilled when their feet touch the sod. Even the hippopotamus gambols when he leaves his concrete house and his feet touch earth and grass.