What the flourishing tradesman writes with pride over his shop, we might in most cases write over our storehouse of antipathies--established in 1720, or 1751. For what good reason we, in 1851, should shudder at the contact of a spider, or loathe toads, it would be hard to say. Our forefathers in their ignorance did certainly traduce the characters of many innocent and interesting animals, and many of us now believe some portions of their scandal. To be a reptile, for example, is perhaps the greatest disgrace that can attach to any animal in our eyes. Reptile passes for about the worst name you can call a man. This is unjust--at any rate, in England. We have no thought of patting crocodiles under the chin, or of embracing boa constrictors; but for our English reptiles we claim good words and good-will. We beg to introduce here, formally, our unappreciated friends to any of our human friends who may not yet have cultivated their acquaintance. The Common Lizard--surely you know the Common Lizard, if not by his name of state--_Zootoca vivipara_. He wears a brilliant jacket, and you have made friends with him, as a nimble, graceful fellow; as a bit of midsummer. His very name reminds you of a warm bank in the country, and a sunny day. Is he a reptile? Certainly; suppose we stop two minutes to remember what a reptile is. The heart of a reptile has three cavities; that is to say, it is not completely double, like our own. It sends only a small part of the blood which comes into it for renovation into the air-chambers--the lungs; while the remainder circulates again unpurified. That change made in the blood by contact with the oxygen of air, is chiefly the cause of heat in animals. Aëration, therefore, being in reptiles very partial, the amount of heat evolved is small; reptiles are therefore called cold-blooded. They are unable to raise their heat above the temperature of the surrounding air. Fishes are cold-blooded, through deficient aëration in another way; in them, all the blood passes from the heart into the place where air shall come in contact with it; but, then there is a limitation to the store of air supplied, which can be no more than the quantity extracted from the water. The temperature of water is maintained below the surface, and we know how that of the air varies, since a certain quantity of heat is necessary to the vital processes; reptiles, depending upon air for heat, hybernate or become torpid when the temperature falls below a certain point. The rapidity of all their vital actions will depend upon the state of the thermometer; they digest faster in the heat of summer than in the milder warmth of spring. Their secretions (as the poison of the adder) are in hot weather more copious, and in winter are not formed at all. The reptiles breathe, in all cases, by lungs; but we must except here those called _Batrachians_, as frogs or newts, which breathe, in the first stage, by gills, and afterward by gills and lungs, or by lungs only.