Page:Popular Science Monthly Volume 15.djvu/250

233 veritable affinity. A popular lesson in natural history, then, teaches us that a whale is a quadruped—that is, apart from the mere etymology of the word, it belongs to the quadruped class. It possesses but two legs, or rather "arms," it is true, and these members do not resemble limbs. But it is a quadruped notwithstanding its deficiencies in this respect; and it agrees in all the characters which are found to distinguish the class to which man himself belongs, that of the Mammalia. These characters it may be advantageous very briefly to detail, by way of preliminary to the general study of whales and their nearest relations. Thus, firstly, they are warm-blooded animals, a statement which must be taken as meaning that their blood is of a temperature considerably higher than that of the medium in which they live. The fish, on the other hand, is a cold-blooded creature. Its temperature is only slightly higher than that of the surrounding water, and in this respect it agrees with all invertebrate animals and with the frogs and reptiles of its own sub-kingdom. Next in order may be noticed the agreement of the whale with the quadruped in the matter of body-covering. The covering of the latter consists of hairs. Although the body of the whale can not be described, by any stretch of the imagination, as having hair, the presence of a few bristles around the mouth extremity sufficiently indicates the nature of its outer garment; while, before birth, the body-covering in some whales is tolerably plentiful, but is soon shed, leaving the hide thick, shining, and hairless. The microscopist might inform us that the blood of the whale presents the same characters as that of other mammals, and possesses red corpuscles or colored bodies, which, unlike those of the fish, reptile, and bird, have no central particle or "nucleus." And while the heart of the fish is a comparatively simple engine of propulsion, consisting of two contractile chambers or cavities, the whale's heart will be found like that of man and other quadrupeds in all essential details of its structure. It is thus a four-chambered organ doing double duty, in that it sends blood not only through the system, but also to the lungs for purification.

The mention of lungs as the breathing organs of whales at once introduces us to a new field of inquiry concerning the habits and life of the aquatic monsters. A popular notion exists that of necessity a water-living animal must be a water-breather. The idea of fish existence and of the manner in which fishes breathe evidently reigns paramount in the present case. That an animal may be completely aquatic in its habits, and yet breathe air directly from the atmosphere, and after a like procedure to that witnessed in human respiration, is a notable fact. A water-newt, despite its aquatic habits, ascends periodically to the surface of the water to breathe; and seals, walruses, and whales agree in that they are truly lung-breathers, and possess gills at no period of their existence. True, a gill differs from a lung only in that it is capable of exposing the blood circulating through it to the