REPTILE. 



549 



other classes, and the prevailing colour is yellow. 

 Then: is very considerable variety in the form of the 

 pupil, la the crocodiles it closes on a vertical line 

 as in the common cat ; in the frogs, and in the 

 geckos among- Saurin, it is four-cornered, and in the 

 common lizards, the chamelion, and the tortoises, it is 

 round. As in the fishes, the crystalline lens in the 

 whole, or, at least in the greater part, is spherical, by 

 which the animals can see under water, whether their 

 general habit is aquatic or not. Those which have 

 two eyelids closing toward each other, have a third 

 or ventilating one as in birds, and some, as the cro- 

 codiles, have a bone in the upper eyelid. In the 

 lizards there are not separate eyelids, but an outer 

 membrane surrounding the whole length, which 

 closes toward the centre by means of a sphincter muscle, 

 much in the same way as the iris closes and contracts 

 the pupil. Thus the eyes of reptiles partake of the 

 structure of those of birds and those of fishes jointly ; 

 they have very great power over the apparatus of 

 their eyes ; and a few, as, for instance, the chamelion, 

 can look two ways at the same time, but whether it 

 can fully see a separate object with each eye is another 

 matter.' Sir Walter Scott was perhaps not aware 

 that he was making a chamelion of Andrew Fair- 

 service, in the novel of Rob Roy, when he repre- 

 sented him as sitting on the sabbath, with one eye 

 intent on the Bible and the other on the bee-hives, 

 equally zealous for the interests of the next world and 

 the present. 



Though many reptiles live in dark and gloomy 

 places, and rarely, if at all, come abroad in the day 

 light, yet it does not appear that the eyes are af- 

 fected by it, because they are well fortified, and there 

 are some which have to bask and sport in the most 

 intense radiance of the tropical sun. In this, as in all 

 other cases, the external action upon them appears to 

 address itself more to their irritability than to their 

 sensation. 



It is very doubtful whether any of their other 

 senses are so acute as the sense of sight. As to 

 hearing, there are few or none of them that have 

 external ears except the crocodiles. That alone 

 would not, however, be sufficient to establish the fact 

 of their being dull hearers ; for there is no reason 

 why the external integument of an animal should not 

 be an organ of the sense of hearing, as well as the 

 tympanum of an ordinary ear is. But, in general, the 

 internal parts of the ear, although never entirely 

 wanting 1 , are less perfect than in those animals which 

 are known to have the sense of hearing the most 

 perfect. In the turtles the tympanum is under the 

 skin, composed of cartilage, and with but a single 

 bone. The saurian reptiles have nearly the same 

 kind of tympanum ; but the bones are more numerous, 

 and there are some additional parts bearing a resem- 

 blance to what are supposed to be the organs of 

 hearing in fishes. The frogs and other members of 

 the order to which they belong have the membrane 

 of the tympanum large and on the same plane as the 

 integuments ; and if abundance of noise in any ani- 

 mals be a sign of hearing, then the frogs can have no 

 lack of that sense ; but the music of their voice is 

 assuredly no argument in favour of their having an 

 ear for music. 



The organs of smelling are also not of the most 

 perfect kind ; and from the places in which many of 

 the species live, they would at all events require not 

 to have very delicate senses in this way. These 



organs chiefly open at the termination of the snout, 

 and extend thence to the mouth by cavities lined 

 with membrane, not unlike the olfactory or pituitary 

 membrane in the mammalia. The external openings 

 are furnished with muscles, by means of which they 

 can be contracted or dilated, and the power of motion 

 in the external nostril is rather an argument in favour 

 of some acuteness of smelling. In some too there are 

 bony plates supporting duplicates of the membranes, 

 and thus increasing tne quantity of its surface. In 

 all of them however the cavities, and consequently 

 the extent of membranous surface, are small in com- 

 parison with those of the mammalia. Yet it is pro- 

 bable that not a few of them depend a good deal 

 upon this sense in the finding of their prey. Many 

 prey during the night, and, climbing trees, eat the 

 eggs and the callow young of the birds which nestle 

 there ; and, as many of the birds nestle in holes of 

 which the openings are small, it is difficult to under- 

 stand how they could be found out, unless by the 

 sense of smelling. 



The degree in which they possess the sense of 

 tasting cannot be very great. The tongue varies 

 much in form. In some, as the crocodiles and the 

 tortoises, it is short and fleshy, and furrowed or 

 covered with small papillae on the upper surface ; but 

 it is fastened to the lower jaw both at the sides and 

 the end, and thus incapable of much motion. In 

 some it is very mobile, in others prehensile to a con- 

 siderable length out of the mouth ; the termination is 

 sometimes an elastic cartilaginous fork, and at other 

 times it is toothed. It is, in many instances, of use 

 in seizing the prey ; but the extent to which it is an 

 organ of taste is not known. The probability is, 

 however, that there is very little taste in any reptile. 

 Their teeth are in no case instruments of mastication, 

 but of prehension, or they assist in working the prey 

 into the mouth, which prey being in the majority of 

 cases swallowed entire, does not admit of being much 

 enjoyed in the way of tasting. 



The system of nutrition is that which next claims 

 our attention. With almost the solitary instance of 

 the green turtle and land tortoise, so much prized by 

 epicures, the reptiles feed upon animal substances, 

 upon animal carrion in a few cases ; but in general 

 they kill their own prey, and in many cases swallow 

 it alive. 



The nutritive system, considered with reference to 

 the organisation, consists of three parts, prehension, 

 swallowing, and assimilating, including under the lat- 

 ter the various steps of digestion. The mouth is the 

 grand instrument of prehension, and it varies much 

 in the armature which fits it for this purpose ; but it 

 cannot be considered as performing any other office 

 than that of simply taking the food and holding it 

 until it is swallowed. 



The tortoises have the mouth the most simple. It 

 is without teeth in any of the order. There are jaw- 

 bones, with intermaxillaries in the upper jaw ; and 

 these jaws are armed with a horny covering which 

 invests the bone like a hoof, and varies a little m 

 hardness. In some specie* too the sides of it are 

 nearly even, but in others they are waved so as to 

 have some slight resemblance to teeth. The anterior 

 part of it is sometimes drawn out into the form of 

 something resembling a bill. The upper jaw of the 

 turtle has no motion upon the skull, but offers a firm 

 resistance for the lower one to close against. The 

 lower jaw is articulated on the skull, and has little or 



