5. The RUMINANTIA.--The Ruminating animals (fig. 63) are those which chew the cud. There are a great many species, and their members are also very numerous. The Ox, and its varieties, the Buffalo, Bison, Yak, &c.; the Deer, Antelopes, Gazelles, &c.; the Sheep, Goat, Giraffe, and Camel, all belong to the Ruminants. These all have hoofs, cloven into two parts; have no incisor (or front) teeth in the upper jaw; and are essentially grazing animals. They have stomachs made up of four compartments; into the first of these (the Rumen) the crude grass enters, and is afterwards returned to the mouth, and again chewed at leisure; the molar teeth, or grinders, are flat, and roughened, so as to effect this purpose; and, that they may not become smooth by wear, the enamel (or hard part) of the teeth is so disposed in various layers, that it is always projecting above the bony part, which wears down first. The Ruminants are gregarious, associating in herds of enormous numbers. Cumming, describes the herds of Springboks, in South Africa, as being in countless thousands, continuing to pass for hours together; and covering the plain as far as the eye could reach. Cattlin, also, describes the American Bison of the Prairies as being congregated in the most surprising numbers. Some of the members of this order are very large and heavy animals. The Cape Buffalo is of enormous strength, and very fierce when attacked. Dr. Livingstone, in his Travels in South Africa, speaking of the Lion, says:--"He seldom attacks full-grown Buffalos; but frequently, when a Buffalo-calf is caught by him, the cow rushes to the rescue, and a toss from her often kills him. One we found was killed thus, and on the Leambye, another, which died near Sesheke, had all the appearance of having received his death-blow from a Buffalo. It is questionable if a single Lion ever attacks a full-grown Buffalo; the amount of roaring heard at night, on occasions when a Buffalo is killed, seems to indicate there are always more than one Lion engaged in the onslaught." [Illustration: FIG. 63--GROUP OF RUMINANTS. 1, Ox (Bos taurus); 2, Sheep (Ovis aries); 3, Red Deer (Cervus elaphus); 4, Camel (Camelus Arabicus); 5, Llama (Pacos).] The Ruminants are the only members of the Mammalia furnished with horns, and some of these are of enormous size; the Elk, Buffalo, and Steinbok, are instances. In the Deer tribe they are shed yearly, and increase in size and in the number of their branches at each fresh growth. The flesh of the Ruminants forms the chief animal food of Man, and some tribes of the American aborigines live exclusively on it.