An acquaintance with the anatomical structure of the vocal organs, together with an understanding of the acoustic laws bearing on their operations, is usually held necessary to a competent knowledge of the principles of voice culture. A rather tedious course of study is indeed demanded for this purpose. But it will be our aim to present this portion of our subject briefly, touching only on those points which are essential to a practical grasp of vocal methods. For a more extended treatment of the anatomy of the organs of voice and breathing any standard text-book of anatomy may be consulted. It is, however, hoped that our outline of the subject will suffice for the purposes of the general reader. As the subject of acoustics is dealt with in Vol. XII, the present chapter does not cover this topic. A sufficient understanding of the laws of vibration and resonance is also assumed on the part of the reader. No man-made musical instrument can compare with the human voice in complexity and delicacy of structure. Yet, so far as the general principles of its construction are concerned, it does not differ materially from the voices of air-breathing mammals and birds in general. In each case the vocal organs form a complex wind instrument, consisting of an air chamber (the lungs), a vibrating mechanism (the vocal cords), and a set of reinforcing resonance cavities. The human voice differs from the voices of other air-breathing animals only in its vastly higher development and complexity. The vocal organs of all the various species of animal life we are now considering were developed as a part of the respiratory system. In the early stages of the evolution of air-breathing animal forms the lungs had only one function, that of supplying air for the oxidizing of the red corpuscles of the blood. No other use was made of the respiratory organs; the breath served no purpose beyond that of furnishing oxygen for the needs of the circulatory system. This was the condition of those forms which were the forerunners of present mammal and bird life. In the course of evolution a gradual change took place in a part of the respiratory tract. This modification was an example of what is called in evolutionary science ‘adaptive change.’ The organs of respiration were modified and developed in such a way that the pressure of the expired air could be utilized in the production of sound. As evolution progressed the organs of voice which thus had their origin took on an ever-increasing complexity of structure. This process of evolution has reached its highest development in man. As a musical instrument the human vocal organs may fairly be said to have reached the point of perfection. I From the anatomist’s standpoint the vocal organs consist of four parts: 1. The lungs, together with the bones by which they are inclosed and the muscles which fill and empty them. 2. The larynx and its appendages.