But supplementary to this, it has hypothetically occurred to me, that as ordinary fish possess what is called a swimming bladder in them, capable, at will, of distension or contraction; and as the Sperm Whale, as far as I know, has no such provision in him; considering, too, the otherwise inexplicable manner in which he now depresses his head altogether beneath the surface, and anon swims with it high elevated out of the water; considering the unobstructed elasticity of its envelope; considering the unique interior of his head; it has hypothetically occurred to me, I say, that those mystical lung-celled honeycombs there may possibly have some hitherto unknown and unsuspected connexion with the outer air, so as to be susceptible to atmospheric distension and contraction.