Gexkral Characters. - 



-REPTILES.- 



-GeSERAL CHARAfTFr.S. 



the animal heat, muscular force, and all the other func- 

 tions dependent upon respiration, will be diminished." 

 Hence it follows that reptiles possess but little power of 

 sustaining muscular action, for though several species 

 are capable of moving rapidly for a short time, it is only 

 when they are suppilied with that degree of temperature 

 externally which is denied them from an internal source, 

 that they are capable of exerting any energy at all. 

 When deprived to a certain extent of external lieat, 

 they then, as has been mentioned above, pass into a 

 state of torpidity or hibernation. In temperate and 

 cool climates, the lizards and serpents retire during 

 \vinter to holes in trees, under stones, beneath dead 

 leaves, or in such like places, where many species, 

 especially serpents, congregate in large numbers, and 

 are found closely entwined together. The land tortoises 

 take refuge from (lie cold in excav.ations, which they 

 often dig for tliemselvcs, and the fresh-water tortoises 

 in holes in the muddy banks, or in the mud at the 

 bottom of their native lakes or rivers. " Here tliey 

 jiass the winter in a state of almost lifeless repose, the 

 functions of life so nearly suspended, that none of the 

 external signs of its existence are visible. Tlie circu- 

 lation is extremely slow, the respiration apparently' 

 altogether stopped, digestion absolutely suspended. 

 The return of the genial warmtli of spring calls them 

 again into action. The circulation is restored, the 

 blood is again fitted for its various offices liy the return 

 of regular respiration, the functions of the digestive 

 organs are again performed, and the animal resumes 

 its former habits, without having undergone any 

 material change."* A similar state of torpidity takes 

 jilace in many reptiles witliin the tropics. This 

 summer torpidity, or, as it may be called, estimition, is 

 governed by the times of drought. Crocodiles or 

 alligators, and large boas, are frer|uently found in a 

 letliargic state in the dry mud, and Humboldt's anec- 

 dote has been freipiently quoted, of an Indian in 

 South America liaving built a hut over the spot where 

 a crocodile lay buried in the hardened clay, and was 

 only made aware of his mistake by the rains moisten- 

 ing the gi-oimd, and bringing tlie huge creature into 

 animation again. 



All Reptiles possess true lungs, and their respiration 

 is exclusively pulmonary throughout the wdiole of 

 their existence. This forms one of the most impor- 

 tant ditlerences which have induced zoologists to sepa- 

 rate the Frogs and Toads, &c., from true Reptiles ; 

 the respiration in these animals, and those arranged 

 along with them, being carried on by means of 

 lirmic/iite or gills during the earlier period of their life, 

 clianging— in some totally, and in others only partially 

 —to the i)ulmonary character, in the adult condition. 

 The limgs are two in nmubcr, right and left, nearly of 

 equal size, except in the serpents, and celhdar or 

 spongy. Tlieir structm-e differs somewhat in the 

 diiieient orders, but in all it is such as oidy to admit a 

 l)ortion of the venous blood from tlie heart, instead of 

 the whole. In the Saurian Reptiles and Serpents, the 

 act of resiiii-ation is carried on mechanically by the 

 action of the ribs, which are more or less free and 



* B^n— British Kei,lih-s. 



moveable, but in the tortoises and turtles the air is 

 introduced into the lungs by a sort of act of deglutition 

 or swallowing. 



The integument or skin of reptiles is dry and liard, 

 and is covered with either liorny plates or with scales, 

 which sti'ucture forms an excellent character for 

 arranging them in two large groups, the scaly and 

 shielded coat of mail reptiles. Their limbs are either 

 four or two in number, or are wanting altogether, at 

 least externally. When present, tliey are in almost 

 all cases very short, and so formed as in most instances 

 to prevent their possessors having a rapid motion. 

 They possess the senses of sight, hearing, taste, smell, 

 and touch. In general the eyes are small, and not so 

 well developed as in the higher classes of animsils. 

 They are largest in the tortoises, crocodiles, and lizaiils, 

 and smallest in tlie serpents. In these latter animtds 

 tliere are no apparent eyelids, and, in consequence, 

 their eyes seem fixed and always wide open. In the 

 lizards we find two Hds; the tortoises and crocodiles 

 have three, whilst the chameleons liave only one, and 

 that a very singular one. Tlie sight itself in general 

 is very acute, for on tliis sense depends their pursuit 

 of food and their perception of the approach of enemies. 

 The organ of hearing is, in general, not so higlily de- 

 veloped in Reptiles as in Mammalia and Birds. They 

 never possess any external ear; and the sense of hear- 

 ing varies a good deal in the difl'erent orders. It is, 

 perhaps, the most obtuse in the tortoise tribe, and the 

 most acute in serpents. In these latter animals and in 

 lizards we see that the sound of music imparts to them 

 great delight, and this is well known to the serpent- 

 charmers of the East. In most cases the internal organs 

 of hearing are entirely covered by the scaly investment 

 of the head; but in the crocodiles, "the external orifice, 

 instead of being thus permanently closed, is provided 

 with a firm, hard, moveable lid, or operculum, by means 

 of which the aperture maybe either stopped or kept 

 open. Thus, while basking on the margin of the river, 

 or lying there in ambush for prey, the crocodile has 

 the power of raising the earlid, in order to listen atten- 

 tively to every noise ; but when lie dives beneath the 

 water, either for safety or to drown the victim he has 

 seized, the entrance of water into tlie auditory cavities 

 is prevented by the firm shutting of the lid, which 

 accurately fits the orifice."* The sense of smell is 

 comparatively feeble in reptiles. Indeed their manner 

 of living woidd lead one to infer that they would have 

 little use for acuteness in that organ. It is niucli the 

 same with the sense of taste. In a large ]iroportion of 

 reptiles their food is swallowed whole and entire, and 

 the structure of the tongue in some of those which tear 

 tlieir prey, as the crocodiles, is such as to .show that 

 that organ is not fitted to be of much use for the pur- 

 pose of tasting. The sense of touch does exist in rep- 

 tiles, but only in a low degree. The skin of their bodies 

 and feet, covered with dry scales or liorny plates, 

 does not seem adapted for the possession of any acute 

 degree of sensation ; and even in those species, such 

 as tlie Geckos especially, in which the toes are dilated, 

 this structure is more for the purpose of enabling 



* MLirtin — History of /Icjjtiles. 



