On the use of the epiglottis / by R. Beveridge.

  • Beveridge, R. (Robert)
Date:
[between 1850 and 1859?]
Catalogue details

Licence: Public Domain Mark

Credit: On the use of the epiglottis / by R. Beveridge. Source: Wellcome Collection.

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    different notes of the voice, for during these movements, the hyoid bone and larynx move together. This simultaneous movement is in fact the only one producible by the muscles called into play ; for the larynx is raised by the action on the hyoid bone of the Digastric and Stylo-hyoid, and perhaps also of the Genio-hyoid and Mylo¬ hyoid muscles*; while it is lowered by the joint action on the hyoid bone and larynx of the omo-hyoid, sterno-hyoid and sterno¬ thyroid muscles, which acting together will draw the whole down in one mass. In deglutition, however, the epiglottis no longer remains vertical, but is bent upon itself in the following manner. The mouth being closed, or the lower jaw fixed, the hyoid bone is raised, and then by a sort of spasmodic action of the tliyro-hyoid muscles, the thyroid cartilage is drawn up by a jerk so as to come upon and slightly overlap the hyoid bone ; by this means the lower part of the epiglottis is made to bear upon the under part of the hyoid bone, and the result is that the upper part is turned backwards,— the aryteno-epiglottic folds are relaxed,—they collapse and fall together, and thus the superior opening of the larynx is closed. The curved position thus given to the epiglottis is only momentarily retained, for its elasticity almost immediately forces down the thy¬ roid cartilage, thus restoring itself to its vertical position, and so tightening the aryteno-epiglottic folds and again opening the superior orifice of the larynx. It would appear as if this movement required the whole power of the muscles in order to overcome the * Note—I put the latter as perh 'ps because I am under the impression that these last do not act but in deglutition. There is this important difference between the raising of the hyoid bone and larynx in speaking or singing and the same movement in swallowing, that in the former the movement is effected while the lower jaw is depressed and the mouth open, while in the latter the lower jaw is always raised and the mouth firmly closed. It would seem probable, therefore, that the ele¬ vation in the former case is performed by muscles independent of the jaw, as the Digastric and Stylo hyoid which act from the cranium, while those taking their fixed point from the jaw will act only in the latter case, when by the elevation and fixing of the jaw they will obtain a firm point of action ; and this is rendered still more probable from the circumstance that in the former case the larynx is inclined slightly backwards, while in the latter case it is decidedly pulled forwards — motions which correspond with the varying directions in which the two sets of muscles act.