These "Side Ring-Pyramid Muscles" ([pl. XI], 3, 1 and 3, 2; see also [pl. IX], 5, 4) are assisted by a single muscle uniting the pyramids behind the elastic band which we have already noticed. This muscle we will call the "Pyramid Muscle" ([pl. XI], 7). By the united action of the muscles which have just been described the vocal chink is thrown in the shape shown on [pl. X], C, and the vocal ligaments are now in a proper position for the production of tone.

Before proceeding any farther it will be well if we once more glance at the muscles with which we have become acquainted, so that we may be quite sure about their functions.

MUSCLES:

I. Governing the Shape of the Vocal Chink.

The Back Ring-Pyramid
Muscles
>[-OPENING
The Vocal Chink.

These are opposed by—

The Side Ring-Pyramid
Muscles, and the Pyramid
Muscles, assisted by the
Shield-Pyramid Muscles
>[-CLOSING
The Vocal Chink.

II. Governing the Pitch of the Tones.

The Ring-Shield Muscles,
assisted by the Back Ring-Pyramid
Muscles
>[- STRETCHING
The Vocal Ligaments.