I stated on page 41 that the vocal ligaments were capable of being stretched by the ring-shield muscles, and that the pitch of the tones produced by their vibrations depended mainly on their tension. As we are now taking note of such movements of the voicebox as may be either seen or felt in the throat, we will take the opportunity of trying whether my statement can be verified. Let the reader, therefore, do as follows:--(1) Place the finger on the shield cartilage, and press it vigorously backward. (2) Sing loudly any high tone that is well within your compass. Hold this tone steadily, and _be quite sure you do not alter its pitch_. (3) Now suddenly remove your finger, continuing to sing as before. What is the result? Your tone is raised by a third, or even more, according to the amount of pressure you exercised on the shield. And how did this result come about? In this way: By pressing the shield backwards you elongated the ring-shield muscles, thereby counteracting their stretching influence, and at the same time slackening the vocal ligaments. The tone you sang while doing this was, we will say C'. By releasing the shield you enabled the ring-shield muscles to contract again, thereby putting the vocal ligaments on the stretch as they were at first. That changed your C' to E', or higher still. Have I proved my assertion? Now one more test, if you please. I pointed out to you on page 34 an opening between the shield and the ring. You will see it on plate V, No. 10. Please sing a low tone; place your finger gently on the shield, and move it downwards. You will soon discover a little hollow which corresponds with the opening I just mentioned, and into which you can easily put part of the tip of your finger. Now sing up the scale, and take care to keep the tip of your finger in the hollow. Remember that in singing up the scale your voicebox will rise, which movement you must follow, or you will lose the place. If you do this carefully, you will find that the hollow gets smaller and smaller by degrees until at last it closes entirely, and you can no longer find a trace of it. Now sing down again, keeping your finger on the same spot. You will soon notice the hollow again, and it will continue to get larger and larger until you arrive at the bottom of your scale. This, of course, is but another way of showing the mechanism by which the pitch of your tones is raised or lowered, and we have proved the same thing by our preceding experiment. But I asked you to try this chiefly because it will enable you to put a check upon my statements with regard to the registers of the voice, a subject which I propose to discuss in another chapter. THE LARYNGOSCOPE, AND HOW TO USE IT.