292 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1923 



tropical mammals. Here also are most of the reptiles. Near by are 

 the monkey house and the bird house, and to the north the antelope 

 house, elephant house, and zebra house. Outdoor yards and cages 

 are placed throughout the park in situations favorable to the comfort 

 and health of the various species exhibited. 



The interest of the public in the National Zoological Park is at- 

 tested by the number of visitors. Over two millions of people now 

 visit the park annually. In 1923 the attendance was 2,393,428, a 

 daily average of 6,558. A large share of the enormous number of 

 tourists to Washington visit the zoo and the sight-seeing cars now 

 regularly include the park in their itineraries. Many people are 

 attracted to the park on account of its walks and drives, and as the 

 entire area is a carefully protected sanctuary for wild birds and 

 flowers, many nature classes from the schools visit it on their field 

 excursions. 



Three great classes of animals — mammals, birds, and reptiles — 

 are represented in the collections maintained in the National Zoo- 

 logical Park. 



MAMMALS 



The mammals (class Mammalia) comprise those creatures com- 

 monly known as " animals." They are usually distinguishable from 

 other vertebrates by numerous well-known superficial characters and 

 are briefly defined technically as warm-blooded vertebrates with 

 hair, and with glands in the female for the secretion of milk for the 

 nourishment of the young. Mammals offer a great range of variety 

 in size, general appearance, and mode of life. The elephant, whale, 

 mouse, shrew, and bat present examples showing extremes in bulk 

 and habit. The vast majority of the mammals usually exhibited in 

 zoological gardens belong to the subdivisions of the class known as 

 the ungulates (hoofed mammals), primates (apes, monkeys, and 

 lemurs), rodents (gnawing mammals), carnivores (flesh eaters), and 

 marsupials (pouched mammals). In the National Zoological Park 

 good collections of numerous species of these groups of mammals 

 may be seen and studied to advantage. 



THE UNGULATES, OR HOOFED MAMMALS 



Modern systematic mammalogists divide the existing " hoofed ani- 

 mals " into four orders — the Proboscidea (elephants), Hyracoidea 

 (hyraxes), Perissodactyla (horses, tapirs, and rhinoceroses), and the 

 Artiodactyla (cattle, sheep, antelopes, deer, camels, swine, and hip- 

 popotamuses). The Perissodactyla are called the "odd-toed" un- 

 gulates, and usually have an uneven number of toes ; as the existing 

 horse with one functional toe, and the rhinoceros with three. The 



