Aristotle On Youth and Old Age,On Life and Death,On Breathing-Part 14

Empedocles also gives an account of respiration without, however,making clear what its purpose is, or whether or not it is universal inanimals. Also when dealing with respiration by means of the nostrilshe imagines he is dealing with what is the primary kind ofrespiration. Even the breath which passes through the nostrilspasses through the windpipe out of the chest as well, and withoutthe latter the nostrils cannot act. Again, when animals are bereftof respiration through the nostrils, no detrimental result ensues,but, when prevented from breathing through the windpipe, they die.Nature employs respiration through the nostrils as a secondaryfunction in certain animals in order to enable them to smell. Butthe reason why it exists in some only is that though almost allanimals are endowed with the sense of smell, the sense-organ is notthe same in all.A more precise account has been given about this elsewhere.Empedocles, however, explains the passage inwards and outwards ofthe breath, by the theory that there are certain blood-vessels, which,while containing blood, are not filled by it, but have passagesleading to the outer air, the calibre of which is fine in contrastto the size of the solid particles, but large relatively to those inthe air. Hence, since it is the nature of the blood to move upwardsand downwards, when it moves down the air rushes in and inspirationoccurs; when the blood rises, the air is forced out and the outwardmotion of the breath results. He compares this process to whatoccurs in a clepsydra.Thus all things outwards breathe and in;- their flesh has tubesBloodless, that stretch towards the body's outmost edge,Which, at their mouths, full many frequent channels pierce,Cleaving the extreme nostrils through; thus, while the goreLies hid, for air is cut a thoroughfare most plain.And thence, whenever shrinks away the tender blood,Enters the blustering wind with swelling billow wild.But when the blood leaps up, backward it breathes. As whenWith water-clock of polished bronze a maiden sporting,Sets on her comely hand the narrow of the tubeAnd dips it in the frail-formed water's silvery sheen;Not then the flood the vessel enters, but the air,Until she frees the crowded stream. But then indeedUpon the escape runs in the water meet.So also when within the vessel's deeps the waterRemains, the opening by the hand of flesh being closed,The outer air that entrance craves restrains the floodAt the gates of the sounding narrow,upon the surface pressing,Until the maid withdraws her hand. But then in contrariwiseOnce more the air comes in and water meet flows out.Thus to the to the subtle blood, surging throughout the limbs,Whene'er it shrinks away into the far recessesAdmits a stream of air rushing with swelling wave,But, when it backward leaps, in like bulk air flows out.This then is what he says of respiration. But, as we said, allanimals that evidently respire do so by means of the windpipe, whenthey breathe either through the mouth or through the nostrils.Hence, if it is of this kind of respiration that he is talking, wemust ask how it tallies with the explanation given. But the facts seemto be quite opposed. The chest is raised in the manner of aforge-bellows when the breath is drawn in-it is quite reasonablethat it should be heat which raises up and that the blood shouldoccupy the hot region-but it collapses and sinks down, like thebellows once more, when the breath is let out. The difference isthat in a bellows it is not by the same channel that the air istaken in and let out, but in breathing it is.But, if Empedocles is accounting only for respiration through thenostrils, he is much in error, for that does not involve thenostrils alone, but passes by the channel beside the uvula where theextremity of the roof of the mouth is, some of the air going thisway through the apertures of the nostrils and some through themouth, both when it enters and when it passes out. Such then is thenature and magnitude of the difficulties besetting the theories ofother writers concerningrespiration.