RESPIRATION

Evening Star, Issue 20995, 8 January 1932, Page 14

RESPIRATION

HOW BIRDS SOAR-HOW FISHES BREATHE

la the vital matter of respiration the influence exercised in the animal economy is much the same in all animals, though in birds there are important modifications. In fishes the air is applied through the medium of the water to the blood in the gills (writes “A.L.E.,” in the Melbourne ‘Age’). The main characteristics in amphibious animals are tha't the whole of the blood does not circulate through the dungs and that they can withstand and not suffer injury, interruptions of respiration. In the insect and lesser tribes there are numerous minute tubes which ramify over the body. These are known to open externally by what are termed stigmata, and by this means the air is received and then expelled. Thus we see an admirable accordance to the modes supporting both life and health over the entire creation. The function of respiration in birds is indeed complex. The lungs, which are placed in close proximity to the breast, are small and somewhat flattened or spread. An examination of the lung setting and the heart reveals a wonderful construction. There is no diaphragm nor alternate lung expansion, as we have been taught obtains in mammalia or animals which suckle their young. Birds’ lungs contain several openings. These are designed to communicate with air cells, which in turn fill the whole cavity of the creature’s body, from the neck to the lower extremities. The cells are filled with air, which enters into and passes out of them through the agency of the lungs._ This action, causes change upon the circulation necessary to the well-being and health of the bird. Birds may at will admit a greater or lesser quantity of air from the lungs into the cells and bones, which are always hollow, that they may increase or decrease ther specific gravity. The skylark is thus able to run swiftly along the ground or soar high into space, irrespective of the density or other atmospheric conditions. Terrestrial or earth-roaming animals cannot poise in the air, however strong in limb or body. Their bones are mostly solid, and on that account they are not endowed with the power of admitting an air supply into the innermost recesses of their bodies. Hawks, eagles, falcons, and other “diving” or “pouncing” birds are supplied with a very remarkable system of air cells, which are also placed in the body and wing muscles. Even in the hollow quill barrels air forces its way at the bird’s will, and it has been accepted as fact that owing to possessing the power to rapidly increase or diminish the air content stored inwardly they are able to instantly erect or compress their plumage. It is the sudden body compression that makes the descent of the hawk, eagle, or skylark so swift. In Australia, where such birds abound, it is easy to study them as they poise in the air. Under such conditions there is a rapid fluttering of the wings while such birds remain quite stationary in midair. When about to “ dive ” or pounce the wings are brought quickly against the sides of the bird, and the observer can actually notice the remarkable body compression, and the bird appears to be narrowed out owing to the expulsion of air. HOW FISHES BREATHE. It was declared by Mr Yarrell, the world’s greatest authority on fishes, that “ they possess two senses in common—that of breathing and that of hearing.” There is great diversity of opinion as to their having the sense of hearing, but that they breathe is certain. An examination of the gills of fishes shows them to be covered with an operculum, or flap. The flap has a fringed edge, and a fine example may be seen in the silver dory. This flap

can be so accurately applied to the part beneath that the gill slit may be entirely sealed up. When the fish, in the act of breathing, wishes water to be applied to the gills, it acts with the muscles of the flap, and so it is rendered convex. Such condition produces a vacuum under the flap, and as the fish is in the water and there is an opening in the mouth communicating with the gills, through which the water rushes, it applies itself to the minute ramifications of blood vessels diffused over the gills. When the air which is contained in the water has served its purpose it is ejected through an air opening at the edge of the operculum. The function of respiration is kept up by a repetition of the process, which renews the water and air supply. A fish will die if placed in water which has been boiled, and so denuded of air ; and when lakes become frozen over it is necessary to break the ice to prevent the fishes from suffocating. Some fishes possess what are known as swimming bladders. In the Australian sea pike they are very large, and are analogous to and servo the same purpose—that of increasing or diminishing their buoyancy, as do the ,air cells in birds. The tetrodon, or Australian toad fishes, have the power to inflate their bodies and remain for hours inflated. It is not an uncommon sight to see them in hundreds floating like - miniature balloons upon the sea after a trawl not has been emptied. During the time they_ remain “ puffed up ” it is an impossibility for their enemies to devour them. Another curious fact is that as long as the toad fishes care to float while inflated they have the extraordinary power of being able to breathe the encased air over and over again without using water. Furthermore, it may remain openmouthed while inflated and not eject the minutest particle of air. The mode of respiration employed by frogs, chameleons, and other amphibian creatures is curious. They do not breathe through their mouths, which are kept tightly closed. They take air through their noses, and the jaw muscles force the air into their lungs. It is then ejected through the nostrils through the aid of the action of the upper abdominal muscles. There is an absence of diaphragm, Being by Nature so arranged, such animals would become suffocated if their mouths remained open. This could easily be proved.