Animals also often thrive in a climate very different from that of their natural habitat. Some animals from warm countries, though kept outside without any artificial heat, get on very well during the severe weather of Philadelphia winters, when the temperature often drops to zero Fahrenheit. For the past two years it has been the custom to put outdoors all monkeys—of value—that are suspected of having tuberculosis. The cheap monkeys are killed. The outdoor monkeys are kept in fair sized cages—five feet square and six feet high—usually singly, though sometimes two are together. The vervet, the grivet, the leonine macaque, the yellow baboon, the Hainan gibbon and many others, have not only survived the climatic conditions but have not succumbed to tuberculosis. South American monkeys do not stand cold as well as Old World monkeys, and cannot be kept out in severe winter weather. The monkeys that are kept indoors during winter have free access to the outside through swinging doors and they often go out voluntarily in the coldest weather. The same is true of other animals. A note made several years ago (February 12, 1914) states: “Temperature last night was 1° F. At 2 P.M. outside temperature 13° F., in carnivora house 25° F., elephant house 38° F., giraffe house 39° F., monkey house 42° F. Two Bengal tigers were voluntarily outside. Monkeys that have been out all winter are: two Barbary apes, Hainan gibbon, lion-tailed macaque, yellow baboon, grivet monkey, pigtailed macaque, and eleven rhesus macaques. All the animals appeared comfortable.” The physical condition of the animal and the kind of cold—damp or dry— have much to do with its ability to stand low temperatures. Monkeys have passed through very severe winters without damage, and subsequently in a less severe winter have had frozen fingers, toes or tail. The size of the cage or pen has not as much effect upon the well-being of the animal as might be expected. Reptiles, birds and mammals do as well in cages and pens of medium size as in very large ones. A deer or antelope in a large enclosure does not use all its domain. It usually has a favorite corner near the food, water and shelter, and stays there. Nor has a large enclosure been found perceptibly to diminish mortality from cage-mates. The stronger will follow the weaker until he gets him, no matter what the enclosure. Even in the large flying cage for birds it is necessary to keep out those of a scrappy disposition. From the point of view of the public small enclosures are more satisfactory.