Prove now yourself what I say, for your own satisfaction in your own case; emit breath by exhalation, and see whether you can continue long without catching back your breath; then again catch it back by inhalation, and see what discomfort you experience unless you again emit it. Now, when we inflate a bag, as you prescribe, we do, in fact, the same thing which we do to maintain life, except that in the case of the artificial experiment our inhalation is somewhat stronger, in order that we may emit a stronger breath, so as to fill and distend the bag by compressing the air we blow into it, rather in the manner of a hard puff than of the gentle process of ordinary breathing and respiration. On what ground, then, do you say, "We suffer no injury whenever we transfer breath from ourselves to any object, nor do we ever remember experiencing any damage to ourselves from inflating a bag, the full quality and entire quantity of our own breath remaining in us notwithstanding the process"? It is very plain, my son, if ever you have inflated a bag, that you did not carefully observe your own performance. For you do not perceive what you lose by the act of inflation by reason of the immediate recovery of your breath. But you can learn all this with the greatest ease if you would simply prefer doing so to stiffly maintaining your own statements for no other reason than because you have made them -- not inflating the bag, but inflated yourself to the full, and inflating your hearers (whom you should rather edify and instruct by veritable facts) with the empty prattle of your turgid discourse. In the present case I do not send you to any other teacher than your own self. Breathe, then, a good breath into the bag; shut your mouth instantly, hold tight your nostrils, and in this way discover the truth of what I say to you. For when you begin to suffer the intolerable inconvenience which accompanies the experiment, what is it you wish to recover by opening your mouth and releasing your nostrils? Surely there would be nothing to recover if your supposition be a correct one, that you have lost nothing whenever you breathe. Observe what a plight you would be in, if by inhalation you did not regain what you had parted with by your breathing outwards. See, too, what loss and injury the insufflation would produce, were it not for the repair and reaction caused by respiration. For unless the breath which you expend in filling the bag should all return by the re-opened channel to discharge its function of nourishing yourself, what, I wonder, would be left remaining to you, -- I will not say to inflate another bag, but to supply your very means of living?