Class-book of physiology : for the use of schools and families : comprising the structure and functions of the organs of man, illustrated by comparative reference to those of inferior animals . 85. All the animals which possess a special organ oirespiration may be divided in two large groups, viz:water-breathing and air-breathing animals. Each of thesegroups also presents two distinctive modifications of therespiratory organs, quite unlike each other. 86. In the lowest group of water-breathing animals, therespiratory organs consist of prolongations of the cutane-ous covering into fringes, such
Class-book of physiology : for the use of schools and families : comprising the structure and functions of the organs of man, illustrated by comparative reference to those of inferior animals . 85. All the animals which possess a special organ oirespiration may be divided in two large groups, viz:water-breathing and air-breathing animals. Each of thesegroups also presents two distinctive modifications of therespiratory organs, quite unlike each other. 86. In the lowest group of water-breathing animals, therespiratory organs consist of prolongations of the cutane-ous covering into fringes, such as are represented in the How is this principle modified in different groups of animals ? How doesrespiration take place in the hydra? What is this kind of respiration called?[n what other orders of animals is this kind of respiration found ? What issaid of its importance in cold-blooded animals ?—in the frog ? In how manylarge groups may all the animals which possess a special organ of respirationbe divided ? What modification in each of these ? Describe the respiratoryorgans in the lowest group of water-breathing animals. Fig. 14.—The Hydra, orFresh-water Polype. RESPIRATION. 49. serpula. {Fig. 15.) In different orders of this group ofanimals, the fringes are found in very different forms. Insome, they are attached to the head, and in others, to theside, and serve the double purpose ofrespiratory and locomotive organs. 87. In fishes, which belong to thehighest group of water-breathing ani-mals, the respiratory organs consist of aseries of arches attached to the head,each of which is supplied with a vastnumber of thin elongated plates, collect-ively forming gills. 88. The gills of fishes are made upof numerous little fibres, set close toeach other, like the barbs of a fibre contains a slender plate ofcartilage, which gives it mechanical sup- Fis- is—the , and enables it to preserve its shape while moved bythe streams of water which are perpetual
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