How do the gills of a fish work?
The breathing process is basically the same in both fish and land dwellers. But one all important factor makes the difference between life and death. We can take our vital oxygen from the air and the fish cannot. We cannot take our oxygen from the water and the fish can. A true fish has a pair of gills, one on each side of his head. Each is covered by a saucer shaped gill case where you would expect to find an ear. The front rim of the gill case is fixed to the head, and the opposite side of the rim opens and closes like a flap. The stiff gill case shelters and protects the true gill which is a mass of fringed tissue. As we breathe, we take in oxygen from the air and return waste carbon dioxide. As a fish breathes, he takes in oxygen from the water and returns waste carbon dioxide. Our air fills countless small pockets in our spongy lungs, and these air pores are lined with the thinnest of thin walls. On one side of these walls is air, on the other side are tiny blood vessels. The busy
