1.Front Corner of the Voicebox (Larynx).
2. Ring (Cricoid) Cartilage.
3, 4. Upper Border of the Ring.
5. Shield (Thyroid) Cartilage.
6, 7. Upper Horns of the Shield.
8. Right Lower Horn of the Shield.
9. Point where the Shield moves upon the Ring.
10. Ring-Shield (Crico-thyroid) Aperture covered by Membrane.
11. Lid (Epiglottis).
12. Windpipe (Trachea).

Plate VI.

FRONT VIEW OF THE VOICEBOX, OR LARYNX.

1, 2.Upper Horns of the Shield.
3.Tongue (Hyoid) Bone.
4, 5.Horns of the Tongue-Bone.
6, 7.Bands uniting the Shield with the Tongue-Bone.
8, 9.Lid.
10, 11.Plates of the Shield.
12.Ring.
13.Elastic Band uniting the Shield with the Ring.
14.Windpipe.

hollow part towards the back, is the Shield cartilage ([pl. V], 5), which consists of two plates united in front at an angle which forms the prominence referred to just now as that corner of the triangular funnel ([pl. V], 1) which may be both seen and felt in the throat, and which is commonly called the Adam's Apple. It protects the interior and more delicate parts of the voice apparatus, from which circumstance it derives its name of shield cartilage. The plates of the shield have each at the back two horns, the upper and the lower. With the upper horns ([pl. VI], 1, 2) the shield cartilage is attached by means of bands ([pl. VI], 6, 7) to the corresponding projections ([pl. VI], 4, 5) of the tongue-bone ([pl. VI], 3), which has the shape of a horseshoe. With the lower horns ([pl. V], 8), of which on our diagram we can only see one, it moves upon the ring cartilage as upon a hinge ([pl. V], 9).

This is a very particular point, and I beg the reader particularly to notice that if the shield cartilage ([pl. V], 5) were gradually drawn downwards and forwards, the space which we now see between the shield and the ring ([pl. V], 10) would get smaller and smaller, until at last it quite disappeared; and the distance between the front of the shield ([pl. V], 1) and the highest part of the back of the ring ([pl. V], 4) would be increased.

I may observe here that authorities differ as to whether the shield moves upon the ring, or the ring upon the shield, and that some maintain the one is drawn down while the other is tipped upward. It is sufficient for our purpose, however, that a movement as upon a hinge takes place, whereby, as explained just now, the distance between the front of the shield and the highest part of the back of the ring is increased.