MAMMALIA 



335 



bottom of the river, but swims. It is thought that it swam from the Con- 

 tinent across to Madagascar, thus populating that island with the genus, 

 fossils of which are found in the swamps. The gap of the mouth is wide and 

 the large teeth are used in cutting the bark from trees, which is a prominent 

 feature of the food. They produce a strange carmine-colored secretion, 

 "sweat," containing small crystals and corpuscles, from the skin. "Like 

 other aquatic animals the nostrils are on the surface of the head and can be 

 closed when under water," where it can remain not over ten minutes, and, 

 after reaching the surface again, it spouts like a whale. It is a dangerous 

 animal to meet, as it cannot only capsize a boat, but even bite out large 

 portions of it and will attack man. 



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Fig. 271. — Hippopotamus and young. (Holder's "Zoology," American 

 Book Co., Publishers.) 



The hog (Suidw) (Fig. 272) has four toes, but only two touch the ground, 

 except in miry places. The nostril is situated at the end of the tough, 

 proboscis-like snout. Hogs are generally covered with coarse hair or bristles. 

 The stomach is simple and the cecum present. The typical genus Sus is 

 found in Europe, northern Africa, Asia, and in the Malay Archipelago. 

 The wild boar is Sus scrofa of Europe. 



The wild hog loves to wallow in the wet ground, but sees to it that 

 "cover is handy." The male is usually solitary, while the female and young 

 go about in groups of about a dozen. In India it makes huts of leaves, 

 grass, and twigs, so interwoven as to be practically rainproof, in which the 

 young are housed for several weeks. The domestic pig has been developed 

 from the wild hog by artificial selection and intercrossing. The African 

 wart-hog, the ugliest of land animals, and Babiru'sa are allied. 



The hog industry in the United States represents hundreds of millions 

 of dollars. One-third of the hogs of the world are produced here. Be- 

 sides the pork used at home, large quantities are exported to Europe. It 



