It will be remembered that Madame Seiler's "second chest" corresponds to the upper chest tones of some writers, and that "falsetto" is equivalent to "middle," as generally employed. Ordinary speech is economical, and a range of very few tones, usually not more than two to four intervals of the scale, suffices, but on the stage, and by some of our best public speakers, twice this range may be exceeded. In nature, the cat, under the excitement of a heated interview with a fellow-vocalist, may pass through an entire octave. SUMMARY. The shape of the resonance-chambers varies in the formation of vowels and consonants, which may be classified accordingly, or according to their pitch. Practical implications for singing and speaking, the learning of foreign languages, the study of dialects, etc. The importance of special attention to those words containing the low-pitched and dark vowels, especially when low in the scale, and when sung _piano_. Overtones, and their bearing on the quality of the voice. The carrying power of the voice, determined by the method of its production, is more important than its volume. The value of practice with the use of a mirror, and of the formation of the sounds in practice with a distinctness in excess of the actual needs of the listener. Ease is essential to art. CHAPTER XVII. THE HEARING APPARATUS AND HEARING IN MUSIC. So important are the ingoing sensory messages (impulses) that originate in the ear, as a guide not only in the appreciation of musical sounds but in those movements on which all musical execution, all vocal effects, whether of song or speech, depend, that we think the reader will welcome a chapter on the ear, even though it be no part of the vocal apparatus proper. The essential mechanism used by Nature to give us the sensation of sound consists of (1) a complicated form of nerve-ending; (2) an auditory nerve leading from, and a continuation, in a certain sense, of, the latter; (3) nerve tracts and hearing centres in the brain. The whole constitutes a very complicated mechanism, but the principles on which it is constructed may be reduced to a few. Mechanical or physical principles, as well as physiological ones, are involved. The entire apparatus has for its purpose the conversion of the vibrations of the air into the vibrations of a fluid, which thus stimulates the end-organ, and brings about those changes in the nerve which result in corresponding changes in the brain, that are associated, in some way we cannot explain, to that state of consciousness we term hearing. Complicated as is the auditory apparatus, it can be readily enough comprehended, if the reader accompany the perusal of the text by an examination of the figures introduced.