All whales, for example, breathe in a very curious way. No doubt you have heard of the "spouting" of these animals, and perhaps you may have seen a picture of a whale lying on the surface of the sea, and throwing up a great column of water from its nostrils, or blow-holes. These pictures, however, are rather exaggerated, for what really happens is this: A whale, as of course you know, often remains under water for a very long time, and when at last it rises to the surface, the air in its lungs is heavily laden with moisture. When the air is discharged through the blow-holes into the cold atmosphere the moisture condenses at once into a kind of misty spray, just as that in our own breath does in very cold weather. This is what one sees when a whale is spouting, although as the animal sometimes begins to blow while its nostrils are still beneath the surface, a small quantity of sea-water may, perhaps, be thrown up too. A whale, if it is not disturbed, will often blow fifty or sixty times in succession. Let us try to explain why it does so. If _you_ try to hold your breath, you will find that it is very difficult to do so for more than three-quarters of a minute. But if, before you make the attempt, you get rid of as much of the air in your lungs as you possibly can, draw in a very deep breath and get rid of that, and then repeat the process about half a dozen times, you will find that you can hold your breath quite easily for at least a minute and a half. The reason is that by breathing so often and so deeply you have purified all the blood in your body, instead of having, as usual, a very large quantity which has done its work, and requires to be refreshed in the lungs before it can be of any further use. Now the whale spouts fifty or sixty times in succession for just the same reason. It is taking a series of deep breaths so that it may purify all the blood in its body, and be able to remain under water for as long a time as possible without having to rise to the surface for air. And, besides this, there is a most wonderful arrangement in its body which enables it to stay below for very much longer than would otherwise be possible. Inside its chest it has a sort of blood-cistern, so to speak, consisting of a number of large vessels, which contain a great quantity of extra blood, besides that which is circulating through the body. This blood, also, is purified when the whale spouts. Then, when the animal has remained under water for some little time, and begins to feel the want of air, it does not rise to the surface at once, in order to breathe, but just pumps some of the extra blood from this curious cistern into its veins and arteries, to take the place of that which is used up and requires to be purified. This it can do over and over again until all the extra blood-supply is used up too, when it is obliged to rise and spout.