The Back Ring-Pyramid} OPENING Muscles } THE VOCAL CHINK. THESE ARE OPPOSED BY-- The Side Ring-Pyramid } Muscles, and the Pyramid} CLOSING Muscles, assisted by the} THE VOCAL CHINK. Shield-Pyramid Muscles } II. GOVERNING THE PITCH OF THE TONES. The Ring-Shield Muscles, } STRETCHING assisted by the Back Ring-Pyramid } Muscles } THE VOCAL LIGAMENTS. THESE ARE OPPOSED BY-- The Shield-Pyramid } SLACKENING Muscles } THE VOCAL LIGAMENTS. =The Pocket Ligaments= (called "False Vocal Cords," pl. XII, 1 and 2) are a pair of horizontal projections running above and parallel with the vocal ligaments (pl. XII, 3 and 4). The pocket ligaments are, like the vocal ligaments, attached in front to the shield and behind to the pyramids. They may be described as two ledge-shaped pads mainly formed of glands. They are very sensitive and movable, and ready on the smallest incitement to meet with great rapidity in order to protect the vocal ligaments from any harm. They must, therefore, be chiefly regarded as safeguards of the vocal apparatus, though it is probable that by breaking the stream of air passing through the chink of the glottis, they also exercise considerable influence upon the _quality_ of the tone emitted. It may be affirmed, however, without the slightest hesitation, that they have absolutely nothing to do with the _production_ of tone. We shall see these glandular ledges again during our observations upon the living subject, and I shall therefore say no more about them at present. [Illustration: PLATE XII. VIEW OF THE VOICEBOX, OR LARYNX, WHICH HAS BEEN CUT OPEN FROM BEHIND. 1, 2. POCKET LIGAMENTS (FALSE VOCAL CORDS). 3, 4. VOCAL LIGAMENTS (VOCAL CORDS). 5, 6. SHIELD (THYROID) CARTILAGE. 7, 8. CARTILAGES OF SANTORINI. 9. LID (EPIGLOTTIS). 14, 10 & 15, 11. FOLDS OF MUCOUS MEMBRANE (ARYTENO-EPIGLOTTIC FOLDS). 12, 13. WEDGES (CUNEIFORM CARTILAGES). 14, 15. CARTILAGES OF WRISBERG. 16, 17. PYRAMID MUSCLE (ARYTENOIDEUS TRANSVERSUS). 18, 19. RING (CRICOID) CARTILAGE. 20, 21. TONGUE (HYOID) BONE. ] The space between the pocket ligaments and the vocal ligaments (pl. XII, 1, 2, 3, 4) is the entrance to two pouches or pockets which extend outwards and upwards. The dimensions of these pockets vary very much in different individuals. As a rule their height does not exceed two-fifths of an inch, so that their terminations do not reach the upper borders of the shield cartilage (pl. XII, 5 and 6). But there are instances in which the pockets are nearly three-quarters of an inch high, and where such is the case they, as a necessary consequence, reach beyond the shield. Sometimes they are so high as nearly to touch the root of the tongue. Their outer walls are chiefly formed of loose fatty cellular tissue, and the pockets are almost entirely surrounded by a large number of small glands.