ON ANIMAL LIFE. 735 



ckntly strong for extracting its own foot! oat of the ordinary nutriment of 

 the species. 



Birds are divided, according to the form of their bills, into six orders: 

 accipitres, as eagles, vultures, and hawks; picae, as crows, jackdaws, hum- 

 ming birds, and parrots; anseres,, as ducks, swans, and gulls; grallae, as 

 herons, woodcocks, and ostriches; gallinae, as peacocks, pheasants, turkies, 

 and common fowls; and, lastly, passeres, comprehending sparrows, larks, 

 swallows, thrushes, and doves. 



The amphibia are in some respects very nearly allied to birds: but their 

 blood is little warmer than the surrounding medium. Their respiration is 

 not necessarily performed in a continual succession of alternations, since 

 the whole of their blood does not pass through the lungs, and the circulation 

 may continue without interruption in other parts, although it may be im- 

 peded in these organs, for want of the motion of respiration. They are very 

 tenacious of life; it has been asserted on good authority that some of them 

 have lived many years without food, inclosed in hollow trees, and ev-en in 

 the middle of stones; and they often retain vestiges of life some days 'after 

 the loss of their hearts. Their eggs are generally covered with a membrane 

 only. They have sometimes an intermediate stage of existence, in which all 

 tlieir parts are not yet developed, as we observe in the tadpole; and in this 

 respect they resemble the class of insects. They are now universally consider- 

 ed as divided into two orders only ; reptilia, as the tortoise, the dragon, or 

 flying lizard, the frog and the toad ; all these have four feet : but the animals 

 which belong to the order serpen tes are without feet. Most of the serpentes 

 are perfectly innocent, but others have fangs,by which they instila poisonous 

 fluid into the wounds that they make. In England the viper is the only; 

 venomous serpent; it is known by its dark brown colour, and by a stiipe of 

 whitish spots running along its back ; but to mankind its bite is seldom, if- 

 ever, fatal. 



The first three classes of animals have lungs, as we have already seen, for 

 respiration, and receive air by the mouth; those which have gills, and 

 red blood, are fishes, residing either in fresh or in salt water, or indiiferently 



