in front, their attachments being close together; posteriorly they are attached to the pyramidal cartilages.  It is necessary, however, to describe a little more fully these attachments.  Extending forwards from the base of the pyramids are processes termed the “vocal processes,” and these processes give attachment to the elastic fibres of which the vocal cords mainly consist.  There are certain groups of muscles which by their attachment to the cartilages of the larynx and their action on the joints are able to separate the vocal cords or approximate them; these are termed respectively abductor and adductor muscles (figs. 5 and 6).  In normal respiration the posterior ring-pyramidal muscles contract synergically with the muscles of inspiration and by separating the vocal cords open wide the glottis, whereby there is a free entrance of air to the windpipe; during expiration this muscle ceases to contract and the aperture of the glottis becomes narrower (vide fig. 10).  But when the pressure is required to be raised in the air passages, as in the simple reflex act of coughing or in vocalisation, the glottis must be closed by approximation of the vocal cords, and this is effected by a group of muscles termed the adductors, which pull on the pyramid cartilages in such a way that the vocal processes are drawn towards one another in the manner shown in fig. 7.  Besides the abductor and adductor groups of muscles, there is a muscle which acts in conjunction with the adductor group, and by its attachments to the shield cartilage above and the ring cartilage below makes tense the vocal cords (vide fig. 5); it is of interest to note that this muscle has a separate nerve supply to that of the abductor and adductor muscles.

[Illustration:  FIG. 5

Diagram after Testut (modified), showing the larynx from the front.]

[Illustration:  FIG. 6

Diagram after Testut (modified), showing the posterior view of the larynx with the muscles.]

On the top of the pyramid cartilages, in the folds of mucous membrane which cover the whole inside of the larynx are two little pieces of yellow elastic cartilage; and in the folds of mucous membrane uniting these cartilages with the leaf-like lid cartilage (epiglottis) is a thin sheet of muscle fibres which acts in conjunction with the fibres between the two pyramid cartilages (vide fig. 8).  I must also direct especial attention to a muscle belonging to the adductor group, which has another important function especially related to vocalisation:  it is sometimes called the vocal muscle; it runs from the pyramid cartilage to the shield cartilage; it apparently consists of two portions, an external, which acts with the lateral ring-shield muscle and helps to approximate the vocal cords; and another portion situated within the vocal cord itself, which by contracting shortens the vocal cord and probably allows only the free edge to vibrate; moreover, when not contracting,