On the physiological action of the muscles concerned in the movements of the lower jaw / by Thomas Brian Gunning.

  • Gunning, Thomas Brian, -1889
Date:
1868
Catalogue details

Licence: Public Domain Mark

Credit: On the physiological action of the muscles concerned in the movements of the lower jaw / by Thomas Brian Gunning. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    12/28 (page 8)
    then slacken as the head is forward of the centre and the atlas supported by the splenii muscles. If the head is in balance any pressure upon the forehead brings the muscles into action to preserve it. The action of the muscles in these movements is but a modification of the service rendered by them in raising the head from the horizontal position, in doing which the muscles at first support more than the weight of the head, for in sup- porting the mastoid processes they support the atlas, and make it a fulcrum between the bulk of the head and the counter-balance at the other end of the lever, but as the body comes upright and the head into bal- ance, the strain upon the sterno-mastoid muscles grad- ually diminishes, until the head is held by the posteri- or muscles, when the spine bears all the weight. [A reference to the figure (froutippiece) •will render this explanation more arparent. The same lignre also illustrates the action of the mnscles of the lower jaw, and confirms the opinions expressed in the subsequent portions of this paper.] The hyoid bone, in addition to the muscles which pass to it from parts above the lower border of the jaw, gives attachment to others, which pass up the front of the neck below the jaw. Of these the sterno-thyroid arises close to the centre of the posterior surface of the upper bone of the sternum, and falling back somewhat as it passes up, is inserted into the side of the thyroid cartilage, from whence the ihyro-hyoid (appearing like a continuation of the preceding) goes up and is inserted into the body and greater cornu of the hyoid bone. The sterno-hyoid arises from the sternum and end of the clavicle and is inserted into the lower border of the body of the hyoid bone. It is separated considerably from its fellow at its origin, but crosses the sterno-thy- roid and approaches it in the middle of its course; it leaves the front of the thyroid cartilage uncovered.