Outlines of human physiology; designed for the use of the higher classes in common schools . because the par vagumdoes not give them off, till it has passed the larynx andentered the chest. In front and somewhat below the larynx, is situateda body, called the thyroid gland, the use of which isnot known. It consists of two lobes, one on eachside, which are united together in the middle. It isvery largely supphed with blood, having four arteries,two from the external carotid, and two from the sub-clavian. There is no evidence that it performs thefunctions of a gland, as no excretory duct has eve
Outlines of human physiology; designed for the use of the higher classes in common schools . because the par vagumdoes not give them off, till it has passed the larynx andentered the chest. In front and somewhat below the larynx, is situateda body, called the thyroid gland, the use of which isnot known. It consists of two lobes, one on eachside, which are united together in the middle. It isvery largely supphed with blood, having four arteries,two from the external carotid, and two from the sub-clavian. There is no evidence that it performs thefunctions of a gland, as no excretory duct has everbeen detected going off from it. It is of a very varia-ble size in different individuals: it is usually larger infem les than in males, and it is the seat of that singularand anomalous disease, so prevalent in some countries,which is known by the name of goitre. The larynx is undoubtedly the organ of voice. Ifan opening be made in the wind-pipe, the voice is lost:17* 198 THE VOICE. if this opening be closed by the hand, or any thing thatshuts it completely, the voice is restored. We see. The larynx and trachea 3oen in front, in thyroid ghuid is shaded. Ji Jhe thyroidcartilage. B ihe cricoid cartilage. C Thetrachea. DD Ihe thyroid gland sealed bflowthe larynx, and embracingtlio upper part of Uiotrachea. this frequently in persons who attempt to commit sui-cide, but who only wound the wind-pipe, or the larynx,without cutting any important blood-vessel. THE VOICE. 199 It is also proved by experiment that the epiglottis isnot concei ned in the production of the voice. An in-cision was made in a living animal between the oshyoides, the bone of the tongue, and the thyroid cartil-age, and through this opening the epiglottis was drawnout: the animal retained his voice. It has also beenascertained, that the voice is not lost when the epiglot-tis is confined or even cut away. Its office seems tobe only to guard the wind-pipe against the introductionof foreign substances into
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