We now proceed to study the Registers of the human voice. A very Babel of confusion exists on this important subject, and we are not only perplexed by a multiplicity of terms, but also by the various and often contradictory meanings attached to them. Thus people talk of chest, medium, mixed, throat, falsetto, and head registers, and these terms being utterly unscientific--_i.e._, being based upon sensations and fancies instead of physiological facts--no one can give a clear and satisfactory definition of any one of them. To bring order into such chaos is an almost hopeless undertaking, and the first step in this direction is obviously to ask ourselves, What is the meaning of the word "Register?" My reply is this: _A register consists of a series of tones which are produced by the same mechanism_. Then comes the question, Can any such registers be demonstrated in the vocal apparatus; and if so, what are the mechanisms by which they are produced? The answer supplied by the laryngoscope is, Yes. There are, broadly speaking, three registers in the human voice, and the mechanisms are plainly visible, as follows:--(1) During the lowest series of tones the vocal ligaments vibrate in their entire thickness (pl. XIV). (2) During the next series of tones the vocal ligaments vibrate only with their thin inner edges (pl. XV). (3) During the highest series of tones a portion of the vocal chink is firmly closed, and only a small part of the vocal ligaments vibrates (pl. XVI). In accordance with these physiological facts, Mr. Curwen, in his admirable book "The Teacher's Manual," calls the registers _the Thick_, _the Thin_, and _the Small_. These names have a scientific basis, and their meaning cannot be misunderstood. They are already familiar to thousands who study music by Mr. Curwen's method, and I have myself made use of them in my lectures at University College and at other places. I shall, therefore, also adopt them in this little work, and hope they will soon find general acceptance among teachers and learners, as thereby a great many misunderstandings will be avoided. * * * * *