Observations on the physiology of the larynx / by John Wyllie, M.D.

  • Wyllie, John.
Date:
1866
Catalogue details

Licence: Public Domain Mark

Credit: Observations on the physiology of the larynx / by John Wyllie, M.D. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    resembled the voice. Feeling satisfied that the true cords could not present any serious obstacle to the exit of air when the glottis is closed, I now drew air backwards through the larynx, in order to test their value as opposing its entrance during attempted in- spiration. I found that by a very slight and easy adjustment of the arytenoid cartilages I could prevent its entrance entirely. The cords did not require to be forcibly pressed together; the circumstances most favourable for obtaining their perfect valvular action were that they should be accurately approximated but not stretched, so that when air was blown upwards through the trachea a low note was produced. In this condition by gently pressing- forward the apices of the arytenoid cartilages the air was completely obstructed. I next proceeded to ascertain the effect of bringing together the false vocal cords (B). These are not so easily brought into contact as the true, and the means adopted were therefore rather more com- plicated. Still keeping the arytenoid cartilages fixed together as before, with a needle and ligature, I passed, in addition, two other needles through the anterior surface of the thyroid cartilage, one on each side of the middle line, just opposite the anterior attachments of the cords, and carefully guided their points backwards to their arytenoid extremities, so that each needle was contained within the free edge of a false ligament. The posterior attachments of the cords were then approximated by pressure between the finger and thumb, and at the same time in their whole length they were brought into close apposition by separating the heads of the needles in front of the thyroid cartilage. On attempting to blow upwards through the trachea, when the parts were so arranged, the closure of the glottis was found to be complete. The simple coaptation of the free edges of the false cords proved itself sufficient to obstruct entirely even a powerful current of air from below. The conclusion to be derived from these experiments is obvious. There is within the larynx a double valve which is capable of con- trolling both the exit and entrance of air. The plan found so com- monly throughout the body in such structures, in the aortic and ileo-coecal orifices, and in the course of the veins, holds good here likewise. In the upper half the resemblance is most obvious. Comparing it with the aortic valve we find the representatives of the sinuses of Valsalva in the well-marked ventricles of Morgagni, whilst the cusps are reproduced in the two folds of mucous mem- brane, whose free edges are known as the false vocal cords. The same design may be traced in the lower half of the valve. When the true vocal ligaments are brought into apposition, no deep sinus is found on either side, but their upper surfaces form together a broad flattened plane slightly hollowed out exterior to the margins of the rima glottidis, and this arrangement, owing to the greater density and mobility of the parts, is found to act as efficiently as the well-marked ventricles and cusps of the upper valve. B