574 LECTURE L1X. 



nished with joints, and worms have nothing but simple tentacula at most 

 in the place of legs. Fishes have cold red blood, which is exposed to the 

 influence of the air contained in water, by means of their gills. The 

 amphibia receive the air into their lungs, but their blood is cold, like that 

 of fishes, and in both these classes the heart has only two regular cavi- 

 ties, while that of animals with warm blood has four ; the whole contents 

 of one pair being obliged to pass through the lungs, in order to arrive at 

 the other pair. Of animals with warm blood, the oviparous are birds, and 

 are generally covered with feathers, the viviparous are either quadrupeds 

 or cetaceous animals, and are furnished with organs for suckling their 

 young. 



Each of these classes of animals is subdivided by Linne into different 

 orders, of which we shall only be able to take a very cursory view. The 

 first class, denominated mammalia, from the female's suckling its young, 

 comprehends all viviparous animals with warm blood. These, with very 

 few exceptions, have teeth fixed in their jaw bones ; and from the form and 

 number of these teeth, the orders are distinguished, except that of ceta- 

 ceous fishes, which is known by the fins that are found in the place of feet. 

 The distinctions of the teeth are somewhat minute, but they appear to 

 be connected with the mode of life of the animal, and they are tolerably 

 natural. The first order, primates, contains man, monkeys, and bats ; the 

 second, bruta, among others, the elephant, the rhinoceros, the ant eater, 

 and the ornithoryhncus, an extraordinary quadruped, lately discovered in 

 New Holland, with a bill like a duck, and sometimes teeth inserted behind 

 it ; but there are some suspicions that the animal is oviparous. The order 

 ferae contains the seal, the dog, the cat, the lion, the tiger, the weasel, and 

 the mole, most of them beasts of prey; the opossum and the kangaroo also 

 belong to this order, and the kangaroo feeds on vegetables, although its 

 teeth are like those of carnivorous animals. The fourth order, glires, com- 

 prehends beavers, mice, squirrels, and hares ; the fifth, pecora, camels, goats, 

 sheep, and horned cattle. The sixth order, belluae, contains the horse, the 

 hippopotamus, and the hog. The cetaceous fishes, or whales, form the 

 seventh and last order ; they reside in the water, enveloped in a thick 

 clothing of fat, that is, of oily matter, deposited in cells, which enables 

 their blood to retain its temperature, notwithstanding the external contact 

 of a dense medium considerably colder. 



Birds are distinguished from quadrupeds, by their laying eggs ; they 

 are also generally feathered, although some few are rather hairy ; and 

 instead of hands or fore legs they have wings. Their eggs are covered by 

 a calcarious shell ; and they consist of a white, or albumen, which nourishes 

 the chick during incubation, and a yolk, which is so suspended within it, 

 as to preserve the side on which the little rudiment of a chicken is situated, 

 continually uppermost, and next to the mother that is sitting on it. The 

 yolk is in great measure received into the abdomen of the chicken a little 

 before the time of its being hatched, and serves for its support, like the 

 milk of a quadruped, and like the cotyledons of young plants, until the 

 system is become sufficiently strong for extracting its own food out of the 

 ordinary nutriment of the species. 



