Elements of comparative zoology (1904) Elements of comparative zoology elementsofcompa00king Year: 1904 FISHES. 321 of the ventral aorta, and contains no valves. After pass- ing through the afferent and efferent branchial arteries (p. 311) the blood is collected in the dorsal aorta and thence distributed to the body. The blood, returning to the heart, bears with it the waste from all parts of the body, and prominent among this is carbonic dioxide; in short, it is what physiologists Fig. 121.—Types of Fish-hearts, a, auricle; b, bulbus; c, conus; v, ventricle. call venous blood. This is for
Elements of comparative zoology (1904) Elements of comparative zoology elementsofcompa00king Year: 1904 FISHES. 321 of the ventral aorta, and contains no valves. After pass- ing through the afferent and efferent branchial arteries (p. 311) the blood is collected in the dorsal aorta and thence distributed to the body. The blood, returning to the heart, bears with it the waste from all parts of the body, and prominent among this is carbonic dioxide; in short, it is what physiologists Fig. 121.—Types of Fish-hearts, a, auricle; b, bulbus; c, conus; v, ventricle. call venous blood. This is forced forward, through the ventral aorta and the branchial arteries, to the gills. Through the thin walls of these it comes in close connec- tion with the water, and the carbonic dioxide is given off, while oxygen, from the air dissolved in water, is taken into the blood, which thus becomes arterial blood, and is distributed to all parts of the system through the dorsal aorta and other vessels. Hence, as will readily be under- stood, the heart of the fishes, in contrast to that of all other vertebrates, receives only venous blood. It is interesting to note why a fish dies when taken from the water. It is simply because it cannot obtain air enough. When the fish is in the water the gills are floated out so that all parts of them are exposed to the stream
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