conditions of something which percusses, something percussed, and a something, that is the air, in which percussion can be made, it might reasonably be assumed, that such creatures only as take in air can have a voice. Now, nature employs simultaneously the air respired for two functions, just as she employs the tongue for taste and for speech; and of these the former is necessary (and therefore imparted to most creatures), and the latter, as an organ for interpretation, is for their higher good; so too does she employ the breath both as necessary for tempering the heat within (as shall be explained elsewhere), and for the production of voice, which is for the welfare of the individual. The pharynx is the organ of respiration, for the sake of which is another part, the lung, and it is owing to this part that quadrupeds have more heat than other creatures.
It is the place about the heart which first needs respiration; and, therefore, it is necessary that the air, during inspiration, should pass inwards; and thus the percussion of the air respired by the living principle in those parts, against the so-called trachea, constitutes the voice. But every sound produced by an animal is not voice, as we have said (for it is possible to produce sound by the tongue, as in coughing), but in order to constitute the voice, there must be a percussing living force, and the sound produced must be expressive of something. The voice is, in fact, a
