Aristotle On Youth and Old Age,On Life and Death,On Breathing-Part 9

Further, the assertion that they draw in air out of the mouth or outof the water by means of the mouth is an impossibility, for, nothaving a lung, they have no windpipe; rather the stomach is closelyjuxtaposed to the mouth, so that they must do the sucking with thestomach. But in that case the other animals would do so also, which isnot the truth; and the water-animals also would be seen to do itwhen out of the water, whereas quite evidently they do not. Further,in all animals that respire and draw breath there is to be observeda certain motion in the part of the body which draws in the air, butin the fishes this does not occur. Fishes do not appear to move any ofthe parts in the region of the stomach, except the gills alone, andthese move both when they are in the water and when they are thrown onto dry land and gasp. Moreover, always when respiring animals arekilled by being suffocated in water, bubbles are formed of the airwhich is forcibly discharged, as happens, e.g. when one forces atortoise or a frog or any other animal of a similar class to staybeneath water. But with fishes this result never occurs, in whatsoeverway we try to obtain it, since they do not contain air drawn from anexternal source. Again, the manner of respiration said to exist inthem might occur in the case of men also when they are under water.For if fishes draw in air out of the surrounding water by means oftheir mouth why should not men too and other animals do so also;they should also, in the same way as fishes, draw in air out of themouth. If in the former case it were possible, so also should it be inthe latter. But, since in the one it is not so, neither does itoccur in the other. Furthermore, why do fishes, if they respire, diein the air and gasp (as can be seen) as in suffocation? It is not wantof food that produces this effect upon them, and the reason given byDiogenes is foolish, for he says that in air they take in too much airand hence die, but in the water they take in a moderate amount. Butthat should be a possible occurrence with land animals also; asfacts are, however, no land animal seems to be suffocated by excessiverespiration. Again, if all animals breathe, insects must do so also.many of them seem to live though divided not merely into two, but intoseveral parts, e.g. the class called Scolopendra. But how can they,when thus divided, breathe, and what is the organ they employ? Themain reason why these writers have not given a good account of thesefacts is that they have no acquaintance with the internal organs,and that they did not accept the doctrine that there is a finalcause for whatever Nature does. If they had asked for what purposerespiration exists in animals, and had considered this withreference to the organs, e.g. the gills and the lungs, they would havediscovered the reason more speedily.