ZOOLOGY. 



their usefulness to man as beasts of burden, 

 docility and strength being combined in them in 

 a remarkable manner. 



Section 2. Artiodactyla in which the toes or 

 hoofs are even in number (two or four). There is 

 no third trochanter to the thigh-bone. When 

 true horns are present, they are paired, and sup- 

 ported by a bony cover. The stomach is com- 

 plex, and the caecum is smalL 



Sub-section Omnivora. 



Family I. HippopotamidcE. This group con- 

 tains but one genus, the Hippopotamus, or River- 

 horse, &c. It is a massive and unwieldy animal, 

 about 1 1 feet in length, with a thick skin, which 

 is furnished with a few hairs. Its muzzle is blunt, 

 and its head large. Three kinds of teeth are 

 present in each jaw, the dental formula being : 



I. 



2 2 ~ I I ,., 66 x- 



C. , M. -: ~ = 36. 



22 I I 66 



The canines are very large, and the crowns of its 

 molar teeth are adapted for grinding roots and 

 vegetable substances. The feet have four toes 



Hippopotamus (Hippopotamus amphibius). 



each. Only one species is known (H. amphi- 

 bius), which is confined to Central and Southern 

 Africa. 



Family 2. Suida, or Pig tribe, are characterised 

 by their thick skin, and by the presence of only 

 two functional toes to each foot, the other two 

 toes being rudimentary, and placed some distance 

 above the ground. There are three sorts of teeth 

 in each jaw, and in the males the canines project 

 forward as tusks. The snout is rounded, and 

 resembles a truncated cone. Their food is prin- 

 cipally vegetable. The domesticated pig is an 

 omnivorous animal. The Wild Boar (Sus scrofa) 

 is a ferocious animal, which abounds in some 

 forests of Europe, and is probably the source 

 from which our domestic breeds are derived. In 

 the Babyroussa (S. babyrussa) of the Indian 

 Archipelago, the upper canines are very long, and 

 grow spirally upwards and backwards, and serve 

 as offensive and defensive weapons. In South 

 America this family is represented by the Peccaries 

 (Dicotyles), which want the external toe on the 



hind-feet, of which the commonest species is the 

 Collared Peccary^ (D. torquatus). 



The fossil Anoplotheria, from the Eocene rocks, 

 exhibited a transition between the Suida and the 

 Ruminantia. They were slender of form, and the 

 dental formula is : 



I. 3 3 7 



C. 



I I' 



77 



Their peculiarity is that the molars come close to 

 the canines, without leaving an interval, a mode 

 of arrangement found nowhere amongst Mammalia 

 except in man himself. 



Sub-section Ruminantia. 



Ruminantia, or Ruminant Animals, are the most 

 natural and best determined group of the mam- 

 malian class. In a typical ruminant (ox, sheep), 

 there are no incisor teeth in the upper jaw, their 

 place being taken by a hardened pad of gum, against 

 which the lower incisors impinge. In the upper 

 jaw there are only six molars on each side, with 

 double crescentic ridges of enamel, which aid in 

 masticating, but no canines. There are eight 

 incisors in the lower jaw, behind which is a space, 

 and then come six molars on each side. The feet 

 are each terminated by two toes and two hoofs, 

 which present a flat surface to each other, appear- 

 ing as though a single hoof had been cleft ; hence 

 the names that have been applied to these animals 

 of ' cloven-footed/ &c. There are also usually two 

 vestiges of lateral toes placed at the back of the 

 foot. 



The name of the order intimates the singular 

 faculty possessed by these animals of masticating 

 their food a second time, or ' chewing the cud.' 

 This faculty depends on the structure of their 

 stomachs, which are four in number. The food, 

 which is cropped by the incisor teeth, is swallowed 

 almost without mastication, and is moistened in 

 the first stomach o\ paunch. It then passes into 

 the reticulum, or honey-comb bag, whose inner 

 surface is divided by ridges into a number ot 

 hexagonal cells (hence the name), where, after 

 being rolled into pellets or cuds, it is returned 

 into the mouth, to be rechewed while the animal 

 is at rest. It is then swallowed a second time, but 

 this time it goes into the omasum, or ' many- 

 plies,' so called because its lining membrane is 

 thrown into folds resembling a book ; finally, it 

 passes into the last cavity, or ab-omasum, and 

 then into the intestine, which is of great length. 

 Taken as a group, these animals are timid, and 

 destitute of powerful means of defence against 

 their foes. When feeding, they are liable to many 

 alarms ; and if they were compelled to spend a 

 considerable time in masticating their food before 

 swallowing it, they would often have to leave their 

 pasture before their wants are supplied. They 

 convey a store of food into .the first stomach, 

 and then retiring to a secure place, they prepare it 

 for digestion at their leisure. 



The Ruminants are, of all animals, the most 

 useful to man. They supply him with a large 

 proportion of his animal food. Some serve him 

 as beasts of burden ; others furnish him with their 

 milk, their tallow, hair, leather, horns, and other 

 useful products. 



(A.) The Camelida:, or Camel tribe, differ from 

 the typical Ruminants in having two incisors in 



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