"He must have air, however, and he is compelled to swallow it in gulps. He closes the mouth, and sucks up a quantity of air through the nostrils, swallowing each draught with a special effort. He cannot take in much air in this way, but he is assisted in breathing by his moist, porous skin, which also absorbs a small quantity of air.
"During the winter, when flies and grubs are not to be found, the frog betakes himself to the bottom of the pond, scoops out a hole for himself in the mud, and there sleeps till the frost and snow have gone.
"All this time his skin has to do the entire work of breathing by taking in air from the water, for the frog cannot breathe under water with his lungs any more than we could.
"Teacher showed us that, even with lungs and skin too, the frog takes in very little air, so little,indeed, that it is not enough to warm his blood. The blood is always cold. We call the frog a cold- blooded animal.
"This explains why the body is not provided with a warm coat, for there is no need to keep the heat in. It has nothing but a naked skin, which always feels cold and clammy to the touch."SUMMARY
