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B. Vertical section through larynx, showing inside. 1. Thyroid cartilage. 2. Cricoid cartilage. 3. Trachea. 4. Hyoid bone. 5. Epiglottis. 6. Vocal cord. 7. False vocal cord. 8. Lining of mucous membrane. The thyroid cartilage consists of two V-shaped pieces, one on either side of the larynx, meeting at their points in front, and each terminating at the back in an upward and a downward projection.
The muscles act on these movable cartilages, and nearly all the changes in the vocal bands are brought about through the alterations in position of the arytenoid cartilages, to which they are attached behind. Before describing the muscles of the larynx, the reader is reminded of the order of structures from above downward, in front, which is as follows: The hyoid bone. The thyro-hyoid membrane.
If we appeal from adult anatomy to embryology the case becomes all the worse for us. Our ear is lodged in the gill-slit of a fish, our jaws are branchial arches, our hyoid bone the rudiment of this system of bones supporting the gills.
From above downward one feels in the middle line the parts in the order previously mentioned, beginning with the hyoid bone. One may learn that the larynx is movable and yielding, a hard structure covered with softer tissues, but what these are, and much more, can only be learned by examination of the larynx after it has been removed from some animal.
If these zoologists see in us nothing more than a mammal with thirty-two vertebrae possessing the hyoid bone and more folds in the hemispheres of the brain than any other animal; if in their opinion no other differences exist in this order than those produced by the influence of climate, on which are founded the nomenclature of fifteen species whose scientific names it is needless to cite, the physiologists ought also to have the right of making species and sub-species in accordance with definite degrees of intelligence and definite conditions of existence, oral and pecuniary.
The third branchial arch is only cartilaginous at the foremost part, and here the body of the hyoid bone and its larger horn are formed at each side by the junction of its two halves. They have been lost long ago. Moreover, the four gill-clefts of the human embryo are only interesting as rudimentary organs, and they soon close up and disappear.
The hyoid bone, or tongue-bone, is that hard structure just above the cricoid cartilage, and which one may easily demonstrate to be much more movable than the larynx itself. The tongue muscles are attached to it above, and from it, below, the larynx is suspended, as already explained.
Now the nine millions of human creatures which we here refer to present at first sight all the attributes of the human race; they have the hyoid bone, the coracoid process, the acromion, the zygomatic arch. It is therefore permitted for the gentlemen of the Jardin des Plantes to classify them with the bimana; but our Physiology will never admit that women are to be found among them.
Division of the carotid artery is fatal, and of the internal jugular vein very dangerous on account of entrance of air. Wounds of the larynx and trachea are not necessarily or immediately dangerous, but septic pneumonia is very apt to follow. Wounds of the throat inflicted by suicides are commonly situated at the upper part, involving the hyoid bone and the thyroid and cricoid cartilages.
He seems, speaking scientifically, to be some sort of Mycetes or Howler, from the flat globular throat, which indicates the great development of the hyoid bone; but, happily for the sleep of the neighbourhood, he never utters in captivity any sound beyond a chuckle; and he is supposed, by some here, from his burly thick-set figure, vast breadth between the ears, short neck, and general cast of countenance, to have been, in a prior state of existence, a man and a brother and that by no means of negro blood who has gained, in this his purgatorial stage of existence, nothing save a well-earned tail.
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