Page:The American Cyclopædia (1879) Volume XIV.djvu/290

 REPTILES terns of classification will be found under HER- PETOLOGY ; the batrachians have been treated under AMPHIBIA, and the anatomical peculiari- ties of the order under COMPARATIVE ANAT- OMY. The number of species of reptiles is about 2,000, or less than that of mammals or birds ; most of them are terrestrial, but some (as the dragons) can sustain themselves in the air like the flying squirrels, and the extinct pterodactyl probably winged its way like the bats ; some live habitually in the water, swim- ming by means of flattened tins (as the turtles), or by a laterally compressed tail (as in croco- dilians) ; the amphisbama and other ophisau- rians dwell in subterranean burrows. They present every degree of speed, from the agility of the lizard to the slowness of the tortoise ; some are fitted for running over dry sand, others for climbing trees, others for ascending smooth surfaces ; the" limbs are not generally adapted for rapid or graceful motions, being short, almost at right angles with the npine, and hardly raising the body during locomotion . enough to prevent the ventral surface from dragging on the ground ; the anterior limbs are the shortest, and the knees and elbows are constantly flexed and far apart longitudinally ; the feet are not adapted for prehension (the chameleon excepted), so that they display lit- tle skill in preparing retreats for themselves or places for their eggs. They are naturally cold- blooded for reasons given ttelovv, and are found in greatest abundance and of largest size in warm climates; under the influence of cold they pass into a lethargic state, and according to Ilumboldt a similar condition befalls the South American orocodilians during the hot- test season of the equatorial regions. The tortoise and the crocodile are sufficiently pro- tected against ordinary enemies ; the lizard darts into its hole, perhaps at the expense of a part of its tail, which is soon reproduced; the great boas prevail over every foe but man; many serpents are armed with poison- ous fangs, rarely used however except on the defensive ; some are covered with bristling spines, like the horned lizards, and are thus saved from predaceous animals. They are of great use to man in destroying noxious insects and other animals ; some, like the chelonians, furnish a wholesome and abundant food, and others supply various articles useful in the arts. They are preyed upon by carnivorous birds, as eagles, storks, cranes, and the ibis, and by such mammals as the ichneumon, hog, and the smaller carnivora ; they are themselves essentially carnivorous, and feed on living prey which they swallow whole, but the ma- rine turtles are principally herbivorous. The osteology of reptiles has been given sufficient- ly in the various articles above referred to. Except in chelonians, the form is generally elongated, more or less cylindrical, with a very long tail ; the feet are absent in serpents and in some saurians, and four in the others ; the skeleton is always osseous, the cranium small, and the facial bones and jaws greatly devel- oped, the latter usually armed with sharp, hooked teeth ; the toes are freely movable, and usually with strong claws, webbed in the crocodiles and turtles. The body is covered with scales, generally appendages of the truo skin ; the overlying epidermis is cast off peri- odically ; the scales are converted into bony plates in the chelonians and crocodiles, and in lizards and serpents are often brilliant with metallic reflections; in the chameleon, anolis, &c., the surface modifications of the skin pre- sent very rapid changes of color, sometimes expressing the anger or fear of the animal, and in some cases enabling them to avoid detection by their enemies. The muscles of reptiles are red, though paler than in mammals and birds; they preserve their irritability for a long time after the death of the animal, in chelonians even after many days ; tortoises have been known to live for 18 days after the removal of the brain, groping blindly about. The brain is small, with cerebrum, cerebellum, and me- dulla oblongata ; they have also a spinal system of nerves, and a sympathetic or ganglionic chain ; in most the spinal marrow is relatively much more developed than the brain, the lat- ter being smooth, without convolutions, the cerebral lobes being the largest ; the cerebral hemispheres contain lateral ventricles, and are larger than the optic lobes, which in fishes constitute the greater part of the brain ; there is no pon Varolii, and the cerebellum is more developed than in fishes. Life seems in a re- markable degree independent of the brain, the class rather vegetating than living, and being comparatively insensible to pain ; they grow slowly and live long, and are exceedingly tena- cious of life ; the intelligence is hardly greater than in fishes. The sense of touch is dull, both active and passive, and whether exercised by the skin, toes, lips, tongue, or tail ; taste must also be dull, as the food is swallowed without mastication, and the sense of smell must be still less. The organ of hearing is less devel- oped than in birds and mammals ; there is no external ear ; the tympanum, where it exists, is bare and almost external, and the internal ear is less developed than in fishes. The eyes are usually small, occasionally absent, flat, with incomplete bony orbits, with lids (except in serpents), and with lachrymal glands. The nasal cavities are large, and always communi- cate with the mouth, and in the crocodiles are very far back. The lungs are sometimes large, extending even through the whole length of the ventral cavity, which has no diaphragm ; in the long-bodied snakes only one lung is active, the other being very rudimentary or absent; these organs are comparatively free, the trachea not divided into bronchi, and the air cells few, large, and freely communicating with each other ; in lizards and serpents the ribs serve for respiration, and in tortoises the scapular arch performs the office of ribs, ac- cording to Van der Hoeven, respiration not