air which is entangled or mechanically suspended in the water. Atmospheric air containing the vitalizing oxygen for the renewal and purification of the blood is the great desideratum on the part of all animals, high and low alike. And the gill and lung, therefore, differ simply in the manner and method in which the blood in each is brought in contact with the air, and not in the essential details of their work. The whales are known to "blow," and the act of "blowing" is simply the act of breathing—to be more particularly noticed hereafter. Thus, a whale or seal would be drowned as certainly as an ordinary quadruped would be asphyxiated, were its periodical access to the atmosphere prevented; and the curious fact may here be mentioned that there are also certain abnormal living fishes—notably the climbing perch and ophiocephali of India—which, to use the words of a writer, are as easily drowned as dogs when denied access to the air. There is little need to particularize any of the remaining characters which demonstrate the whale's relationship to mammals, and its difference in structural points from the fishes. The young whale is thus not merely born alive, but is nourished by means of the milk-secretion of the parent, and this last evidence of direct connection with higher animals might of itself be deemed a crucial test of the place and rank of the whales in the animal series.
But, granting that in the whales we meet with true quadrupeds, it may be well to indicate the chief points in which they differ from their mammalian brethren at large. It may be admitted, at the outset, that they present us with a very distinct modification of the quadruped type. Their adaptation to a water-life is so complete, in truth, that it has destroyed to a large extent the outward and visible signs of their relationship with mammals. The body is thoroughly fish-like and tapers toward the tail, where we meet with a tail-fin, which, however, is set right across the body, and not vertically as in the fishes. This latter difference, indeed, is a very prominent feature in whale-structure. The limbs, as already remarked, are represented by the two fore-limbs alone. No trace of hinder-extremities is to be perceived externally, and the anatomical investigation of the skeleton reveals at the best the merest rudiments of haunch-bones and of hind-limbs in certain whales, of which the well-known Greenland whale may be cited as an example. A distinct character of the whales has been found by naturalists of all periods in the "blowholes" or apertures through which the whale is popularly supposed to "spout." Thus we find on the upper surface of the head of a Greenland whale a couple of these "blowholes," or "spiracles," as they are also called. These apertures exist on the front of the snout in the sperm whales, while in the porpoises, dolphins, and their neighbors the blowhole is single, of crescentic shape, and placed on the top of the head. It requires but little exercise of anatomical skill to identify the "blowholes" of the whales with the nostrils of other animals; and it becomes an interest-
