One general trouble lies at the bottom of all the throat ailments which follow on a wrong use of the vocal organs. This is a state of muscular strain suffered by the delicate muscles of the larynx. Every incorrect manner of producing vocal tone imposes an excessive degree of effort on these muscles. On the practical side the difference between the correct production of tone and any wrong use of the voice may be stated thus: When the voice is correctly used each tiny muscle of the larynx exerts exactly the right degree of effort in its contraction. To just this amount of exertion the muscles are fitted by Nature and in it they find their normal and healthful exercise. Incorrect tone production, on the other hand, always involves an excessive expenditure of effort on the part of the laryngeal muscles. The throat is in a state of muscular stiffness, in which all the muscles are contracted with more than their normal and appropriate degree of effort. Muscular stiffness is indeed possible in any part of the body. It can be well illustrated as follows: Take a pencil and a sheet of paper and copy a few lines of what you are reading; grasp the pencil with all the strength of your fingers and exert all the power of your hand and arm in forming the letters. You will find that your arm and hand tire after a few minutes of writing in this manner. This follows from the expenditure of vastly more effort than is required for the purpose of writing. All the muscles of the body are arranged in opposed pairs and groups. As your hand rests on the table, the contraction of one set of muscles brings the thumb and the first two fingers together so as to grasp the pencil. An opposed set will, by their contraction, spread these fingers apart, and the pencil will be released. If, now, both these sets of muscles are contracted at the same time the pencil is held stiffly, and the hand moves to form the letters only by the exertion of considerable effort. The muscles themselves are stiffened by this simultaneous contraction of opposed pairs and groups.