Bruce Leavitt age 13, of Westbrook
Why can’t a fish breathe air?
When it comes to breathing, a frog has more fun than anybody, He can breathe sitting on the bottom of a cool pond. He can also breathe basking high and dry on a warm rock. The poor fish can breathe only in the water and you can breathe only in the air, The frog breathes air with his lungs and he dissolves oxygen from the water with his special skin: The fish breathes water with his gills and you breathe air with your lungs. It's too bath but lungs refuse to breathe water and gills refuse to breathe air.
This is rather strange, for gills and lungs are very much alike, A tree breathes air. 'But your breathing is more like the breathing of a fish than it is like the breathing of a tree. Though, of course, all breathing; is taking useful oxygen and returning useless carbon dioxide, The tree breathes oxygen directly from the air through countless tiny pores all over the surface of leaves and stems. Gills and lungs are specialized breathing organs that work very much alike.
Lungs are bags of spongey tissues. As the breathing muscles work! tiny pockets fill with air and empty. The lungs swell up and shrink like a pair of bellows. Reliable muscles do this job day and night without being told. The air inside the little pockets comes very close to red blood corpuscles. For here in the lungs the tiny blood vessels are very close to the surface. Only a filmy membrane separates them from the air.
In the lungs, the red blood cells are at the end of a work shift. They have been around the body delivering fuel and collecting ashes. The ash from the body's slow burning is carbon dioxide gas. The red cells dump‑this into the air pockets. The muscles squeeze the bellows and out goes a breath of used up air. The lungs open and fill with fresh air teeming :with oxygen„ The red corpuscles grab this fuel through the tiny cell walls and flow on their way to deliver it around the body.
The fish's blood also circulates delivering the same kind of fuel and collecting the same kind of ashes. The red blood cells can take in oxygen and give up and give up carbon dioxide, Tiny blood vessels carry these red cells to the surface in the gills, But in order to breathes the gills must be forever moist. For they can only take in oxygen when it is dissolved in water, The frog can only breathe through his skin when the oxygen is dissolved in moisture, His lungs can breathe only dry, gasy oxygen from the air.
The fish does not fill and empty his gills like a pair of bellows. He keeps the water carrying the oxygen flowing through in a constant stream. Watch him forever opening and shutting his mouth. He is not swallowing all that water: It goes back through the gills and out the gill slits. The gill slits are those, two round flaps where you would expect the fishes ears to be just like the rest of us,, the fish must go on breathing all the time, Our kings go on working automatically even while we sleep. Day and night the fish opens and closes his mouth sending water carrying free oxygen through the gill tissues, Lungs can use only dry oxygen from the air. Gills can use oxygen when it is dissolved in water, For this reason we cannot breathe under water ‑ we drown. A fish cannot breathe in the air ‑ he suffocates,