550 



REPTILE. 



no motion, except opening and shutting ; but in some 

 of the species it shuts with great force, and when 

 once shut it is difficult to be opened against the will 

 of the animal. The horny mandibles of the turtles 

 can readily divide substances, some of them even a 

 cable : and therefore the strength of their muscles is 

 thrown upon those that close the jaws, rather than 

 on those that aid in swallowing. 



The mouth shuts in the same way in the Sauria, 

 but they are furnished with teeth, and the jaws are 

 in general very much produced ; and the motions of 

 them contribute both to prehension and swallowing. 

 Among the most formidable mouths in this order are 

 those of the crocodiles, though some of the extinct 

 species show by the remains that they had been 

 animals of most comprehensive gape. 



The old belief was, that the jaws of a crocodile 

 shut in the opposite way to those of any other ani- 

 mal, by the upper jaw moving and the lower one 

 being fixed ; but the fact is, that both jaws move, 

 and thus the mouth is opened or shut with very 

 great celerity. The lower jaw is not articulated on 

 the skull as in the turtles, but on the upper jaw. 

 That jaw is very long, and the skull, which is small, 

 is lodged in the fork formed by the two maxillaries, 

 and carried with them in any motion they may have. 

 It is this enlargement of the maxillaries, by the way, 

 which changes the round head of the young crocodile 

 to the flat head of the old one. This long upper jaw 

 can be elevated or depressed by the motion of the 

 whole vertebra) of the neck, and partially by those of 

 the back also, so that the face of it in which the teeth 

 are may be brought to the perpendicular, or even to 

 incline a little backwards. This has the same appear- 

 ance, and also produces the same effect, as if the upper 

 jaw had a motion on the skull, and it offers a firm 

 resistance to the lower jaw in closing the mouth, which 

 could not be obtained if the upper jaw had a motion 

 on the skull. Indeed if both jaws so moved, the bite 

 of the animal would be feeble and unsteady. The 

 lower jaw is articulated, on the upper one, and opens 

 from it and shuts against it in the same manner as if 

 the upper did not change its position. The advantage 

 which the animal draws from this is the ability of 

 biting upwards, or with the line of the closed mouth at 

 right angles to the surface of the water. Its prey is 

 often on the surface, and thus it can Jie in wait with 

 the snout above the surface, and thus make a more 

 certain capture. Its teeth are formidable, but they 

 are not capable of dividing a substance, and therefore, 

 vis the rnouth does not dilate beyond the measure of 

 the jaws, the animals are said to bury their larger prey 

 untii it becomes tender enough to shake to pieces. 



The other saurian reptiles have much less power in 

 the bite than the crocodile tribe, but some of them 

 have teeth in the palate which aid in the operation of 

 swallowing. The tongue of the chamelion is one of 

 the most curious prehensile instruments in the whole 

 class of reptiles. It is nearly cylindrical, and about 

 the thickness of a goose-quill, rather thicker at the 

 point than in the basal part. When in a state of re- 

 pose, it is drawn into a sheath in the posterior part of the 

 mouth ; but when used, it is projected with great cele- 

 rity to the length of five or six inches, and at the same 

 time the distal portion becomes covered with a viscid 

 secretion. It seldom fails in killing and attaching the' 

 insects at which it is directed, and then it is with- 

 drawn, and by its contraction assists iu swallowing 

 the prey. 



The entrance to the gullet is simple in reptiles, 

 and the gullet itself is wider in proportion than it is 

 in animals which can masticate, or even bruise the 

 food with the mouth. In many it is beset with pa- 

 pillae, having their points directed downwards, and in 

 most there are longitudinal folds, which by spreading 

 to receive the food, and closing after it, facilitate its 

 passage into the stomach. 



The stomach in reptiles varies very considerably 

 in shape, and sometimes it is doubled back in a curve, 

 but is in all cases a simple stomach ; and though the 

 intestinal canal varies in form in the several members 

 of the order, it may in all cases be said to be with- 

 out csecal appendages. The progress of digestion, 

 like that of most of the functions of these animals, 

 appears to be but slow ; and the action of the gastric 

 juice is chiefly confined to the stomach, the solvent 

 power of the gullet, and whole internal membrane 

 from the mouth down to the stomach in which the 

 first stage of assimilation is completed, being confined 

 to the ophidian reptiles, the notice of which we shall 

 take by itself for the reason already stated. 



But though the process of digestion appears to go 

 but slowly on in the generality of reptiles, there arc 

 many of them which are exceedingly voracious when 

 they do eat. In most cases the food consists of 

 worms, insects, mollusca, and other small animals, 

 though some take larger prey. The turtles live on 

 some species of sea-weed, which grow only in the 

 warmer latitudes ; and is, from their feeding upon 

 it, called turtle-weed, or turtle-grass ; and the land 

 tortoises eat the succulent leaves of plants, being 

 particularly fond of lettuce, though their meals of it 

 are taken at long intervals. Some of the species 

 gorge themselves to the throat, and part of the prey 

 which they have seized, but have not room to swal- 

 low, occasionally escapes unhurt from their mouths, 

 and regains the place of its natural enjoyment. 



Notwithstanding the voracity of some of these 

 creatures under particular circumstances, their absti- 

 nence under others is equally wonderful, if not more 

 so ; and this is increased by the fact that long absti- 

 nence in them is not attended with the same " tailing 

 off in flesh," which is a concomitant of scanty or poor 

 though regular fare in animals of more rapid circula- 

 tion, and more energetic vital powers. Hybernation 

 is not necessary to this ; for turtles and tortoises, 

 alive the while, have existed a year, or even a year and 

 a half, without taking any food ; and the turtles 

 which are brought from the West Indies to " banker 

 out the wits" of the ventricular devotees in England, 

 keep their flesh as well by simply tying up the mouth 

 as if they had the free range of their own favourite 

 weed in the sunny latitudes of the Atlantic. Nor is 

 the power of living without food, and, singular to say, 

 increasing in size under this privation, by any means 

 confined to the turtle, or to the reptiles of warm cli- 

 mates. The common newt of our own country will 

 live without food for a month or two ; the chamelion 

 and the salamander for more than half a year ; that 

 singular creature, the proteus, for two or three years ; 

 and the common toad for a period, the length of 

 which has not yet been determined. 



The part of the subject which next demands a 

 little of our attention is what may be regarded as the 

 most essential part of the vital system c. f reptiles, namely, 

 their circulation, and, closely connected with that, 

 their respiration, or the extent to which they require 

 the circulating blood to be purified ai;d renovated by 



