. Animal physiology. Physiology, Comparative. RESPIRATORY ORGANS OF AQUATIC ANIMALS. 271 the gills composed of a collection of little leaf-like folds, placed on a stalk (6, fig. 154); they are inclosed in a cavity which is covered-in by the mantle ; and the walls of this cavity have the power of alternately dilating and contractmg, so as to draw-in and expel water. It communicates with the exterior by two orifices, one of which, o, a wide sht, is for the entrance. Fig. 154.—Gills of Poulp. of water; whilst the other, t, is tube-like, and serves not only to carry-off the water that has passed o
. Animal physiology. Physiology, Comparative. RESPIRATORY ORGANS OF AQUATIC ANIMALS. 271 the gills composed of a collection of little leaf-like folds, placed on a stalk (6, fig. 154); they are inclosed in a cavity which is covered-in by the mantle ; and the walls of this cavity have the power of alternately dilating and contractmg, so as to draw-in and expel water. It communicates with the exterior by two orifices, one of which, o, a wide sht, is for the entrance. Fig. 154.—Gills of Poulp. of water; whilst the other, t, is tube-like, and serves not only to carry-off the water that has passed over the gills, but also to convey away the excrements, and the fluid ejected by the ink-bag. This is called the funnel. 317. In Fishes, the gills are composed of fringes, which are disposed in rows on each side of the throat, and are covered by the skin. The cavity in which they lie has two sets of apertures; one communicating with the throat, and the other opening on the outside. In the Fishes with a car- tilaginous skeleton, we usually find as many of these external orifices as there are rows of gills; thus in the Lamprey there are seven, as shown in the succeeding figure (a). But in Fishes with a bony skeleton, there is usually but a single large orifice on either side; and this is covered with a large valve-like flap, which is termed the operculum or gill-cover. A continual stream of water is made to pass over the gills by the action of the mouth, which takes-in a large quantity of. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carpenter, William Benjamin, 1813-1885. London : H. G. Bohn
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