33. Nature herself teaches us this in the case of infants. For they first exercise themselves in the sounds of speech and so learn to speak. Thus these sounds of speech are a kind of practice, and a school for the voice. Let those then who want to learn to take heed in speaking not refuse what is according to nature, but let them use all watchful care; just as those who are on a watch-tower keep on the alert by watching, and not by going to sleep. For everything is made more perfect and strong by exercises proper and suitable to itself.