I will now consider at greater length each part of the vocal instrument.




I. THE BELLOWS


[Illustration: Fig 1]

[Description: FIG. 1.--Front view of the thorax showing the breastbone, to
which on either side are attached the (shaded) rib cartilages. The
remainder of the thoracic cage is formed by the ribs attached behind to the
spine, which is only seen below. The lungs are represented filling the
chest cavity, except a little to the left of the breastbone, below where
the pericardium is shown (black). It can be seen that the ribs slope
forwards and downwards, and that they increase in length from above
downwards, so that if elevated by the muscles attached to them, they will
tend to push forward the elastic cartilages and breastbone and so increase
the antero-posterior diameter of the chest; moreover, the ribs being
elastic will tend to give a little at the angle, and so the lateral
diameter of the chest will be increased.]

The bellows consists of the lungs enclosed in the movable thorax. The
latter may be likened to a cage; it is formed by the spine behind and the
ribs, which are attached by cartilages to the breastbone (sternum) in front
(_vide_ fig. 1). The ribs and cartilages, as the diagram shows, form a
series of hoops which increase in length from above downwards; moreover,
they slope obliquely downwards and inwards (_vide_ fig. 2). The ribs are