556 



REPTILE. 



beaks and claws of birds, or in the nasal armature of 

 the rhfuoceros. All these are oF a substance very 

 nearly of the same nature as hair or feathers, and 

 always of a h'brous texture, capable of being divided 

 longitudinally into threads or fibres. All the ap- 

 pendages to the mammalia, and generally also to the 

 birds, are much more easily split longitudinally than 

 they are divisible in the cross direction. This is per- 

 haps more strikingly the case in the nasal horns of 

 the rhinoceri, than in any others ; but it holds in all 

 of them that can be considered as the products of an 

 epidermis capable of producing hair or feathers under 

 other circumstances. The same character holds in 

 the plates of baleen, with which the mouths of the 

 whalebone whales are armed all clearly showing 

 that, if the general habit of the class of animals is 

 to produce a detached fibrous covering, that Covering 

 when it comes in solid portions will follow the same 

 general law. It must not be supposed that the 

 broad antlers of the hinds of deer are an exception 

 to this, for they are really not horn, though they are 

 called "horns:" they are bone, the produce, not of 

 the epidermis of the heads of the animals, but of the 

 bones of the same. 



There is not the slightest tendency to the produc- 

 tion of hair, wool, or any other fibrous matter in the 

 epidermis of any of the reptiles ; and, therefore, the 

 appendages to their skins, w hether they be great and 

 strong plates, as in the Chelonia, or scales of various 

 sizes, as in the different genera of the Sauria, are 

 never of a fibrous structure. They have various de- 

 grees of hardness and tenacity ; but they will break 

 nearly equally in all directions, and they are not sub- 

 ject to those markings by the application of heat 

 which apply to true horn. This, besides its beauty, 

 is one of the recommendations of tortoise-shell as a 

 material in some of the ornamental arts. 



But it must be admitted that even in the Chelonia 

 the solid plates are produced rather from the cutis, 

 than from the cuticle ; for although the body within 

 them is invested in a very perceptible cuticle, there is 

 also another fine membrane without ; so that, if the 

 expression may be admitted, the shield and breast- 

 plate of these animals are produced between the 

 folds of a sort of double epidermis. If the matter, 

 which we call the shell, is very strong and compact, 

 as it is in the greater part both of the land tortoises 

 and the sea turtles, then the membrane over it is very 

 thin, and apt to be obliterated ; but, if what we call 

 the shell is of a weaker consistency, then it is covered 

 with a tough and strong leathery envelope ; and it is 

 not a little worthy of remark, that the turtles which 

 have this soft and pliable shell and leathery covering 

 are by far the most active and ferocious of the whole 

 order. 



In most of the Sauria there is the same complica- 

 tion of the integument. There is one epidermis in- 

 vesting the true skin ; upon this there are scales or 

 horny tubercles of some kind or other, and over these 

 again there is a second epidermis. The crocodiles 

 and some others have broad horny plates, and others 

 have the scales distributed in bands, variously dis- 

 posed on the different species. The Batrachia, in 

 general, have the skin soft, and without any horny or 

 scaly appendages ; and although the old and foolish 

 fable has it that there is a hard substance in the en- 

 velopes of the head of the toad, which has great 

 medicinal virtues, the saying, like many others of the 

 same sort, is totally without foundation. 



In the Sauna there are often very powerful muscles 

 immediately under the skin which can produce con- 

 siderable motion in that, while they show the close 

 connexion which it has with the parts underneath. 

 In the Chelonia, both the shield on the back and the 

 breastplate on the under part, consist of a number of 

 pieces, which contribute much to the strength of the 

 whole. These, in some cases, touch at their edges, 

 and, in others, they overlap. The shield or upper 

 defence is the more perfect of the two. It consists 

 of a separate row of plates or separate pieces, more 

 or less firmly attached to each other, which form the 

 middle or central part, along the mesial line of the 

 vertebra 1 . Immediately in contact with these at the 

 sides there are others, which with them make up the 

 disc of the shield ; and external of these there are 

 still others which compose the margin, and approach 

 the sides of the breastplate. This shield on the back 

 of these reptiles is united to the breastplate on the 

 under part only at the middle of the sides ; and 

 separate at the fore and hind parts, for the action of 

 the head and fore paws at the former, and for that of 

 the tail and hind paws at the latter. 



It does not appear that, under any circumstances, 

 the Chelonia ever change the coverings of their bo- 

 dies ; but the Sauria and Batrachia do, especially 

 when they are in the young state. In them, how- 

 ever, the old skin is not cast at once, as it is in the 

 Ophidia, of which we shall speak in another place ; 

 for it comes off gradually in patches, and the animals 

 are not so much weakened by the operation as those 

 are which moult the entire covering at once. 



The mode of reproduction in animals, and the 

 number of their young, are points of great importance 

 both in understanding their own physiology, and in 

 tracing their connexion with the rest of nature. 

 Reptiles of all orders are in two sexes, without her- 

 maphrodites. All the Chelonia, Sauria, and Batrachia, 

 with the exception of the salamanders in the latter 

 group, are oviparous ; and the number of their eggs 

 in a season may much exceed those of birds. They 

 do not, however, pay much attention to the eggpi 

 after they are extruded ; and, therefore, both eggs 

 and young fall a prey to many enemies. The eggs 

 of the Chelfmia and Sauria resemble the eggs of birds, 

 only there is much less lime in the shell, and the 

 white is gelatine, not albumen, so that the eggs do not 

 boil hard. The eggs of the turtles are much es- 

 teemed as food, and those of the crocodiles are said 

 to be nutritious ; but they have a musky smell. All 

 reptiles which are produced from "eggs with a firm 

 covering come out of the shell in the same form which 

 they are to preserve during their lives ; and it does 

 not appear there is the same limit to their subsequent 

 growth as is found among mammalia and birds. The 

 Batrachia undergo a metamorphosis, and some of them 

 have curious modes of bringing the eggs to maturity, 

 an account of which will be found on looking back to 

 the article FROG, in this work. 



We have already casually alluded to the readiness 

 with which all reptiles yield to a reduction of tem- 

 perature, and pass into the hybernating or dormant 

 state. The readiness with which they pass into this 

 state, under comparatively little reduction of tempe- 

 rature, is a great advantage to them in the way of 

 preservation. The effect of reduced temperature, 

 equally affecting all its body, and accompanied by 

 abstinence from food, is to produce a tendency to the 

 dormant or hybernating state in every animal ; oiJy 



