At least one writer on voice-production, Prof. Wesley Mills, appears to have doubted the correctness of the old and oft-repeated theory. "Allusion must be made," he writes in "Voice-Production in Singing and Speaking," "to the danger of those engaged in mathematical and physical investigation applying their conclusions in too rigid a manner to the animal body. It was held until recently that the pitch of a vocal tone was determined solely by the number of vibrations of the vocal bands, as if they acted like the strings of a violin or the reed of a clarinet, while the resonance chambers were thought to simply take up these vibrations and determine nothing but the quality of tone.... It seems probable that the vocal bands so beat the air within the resonance chambers as to determine the rate of vibration of the air of these cavities, and so the pitch of the tone produced." This at least shows dissatisfaction with the old theory and attaches some share of their due importance to the resonance cavities, but it still is far from describing the correct phenomenon of voice-production. Show a lateral section of a larynx to a trumpet or horn player and he will at once recognize its similarity to the cupped mouthpiece and tube of trumpet or horn, the cup in the larynx being formed by the ventricles or pockets above the vocal cords. Extend the picture so that it includes not only the larynx but the resonance cavities of the head as well, and the cornet, trumpet or horn player will recognize the similarity to the tube of his instrument as it turns upon itself. The manner in which the lips shape themselves as the player blows into the instrument, the form and size of the cup, the gyration and friction of the air within it and within the bent portion of the tube, determine the pitch and the quality of the tone that issues from the bell of the instrument. The shape assumed by the lips, which are capable of many exquisite variations in shape, conditions the form of the air-column as it enters the cup of the trumpet or horn. This I believe to be one important function performed for the larynx by the vocal cords, which Mackenzie, with an aptness he could not have appreciated, called the lips of the glottis. They are, in fact, the lips of the essential organ of voice, the larynx. If they are looked at from below they will be seen to be bevelled, and their resemblance to lips even more striking.