Treatment of fracture of the jaw : with critical remarks / by Thos. Brian Gunning.

  • Gunning, Thomas Brian, -1889.
Date:
1880
Catalogue details

Licence: Public Domain Mark

Credit: Treatment of fracture of the jaw : with critical remarks / by Thos. 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.

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    anterior portions of the two muscles, and a firm investment for the other muscles of this region. This muscle is peculiar in not being inserted into the hyoid bone, but attached to it by a loop; this allows the muscle to act without interfering too much with the hyoid bone. I he digastric muscle has not, however, that freedom which is attributed to it as a reflected cord, for its aponeurotic connection with the hyoid bone and adjoining muscles prevents it from sliding through the loop which attaches it to the hyoid bone. The digastric muscle is set down as drawing the hyoid bone back- ward and forward in deglutition, and as depressing the jaw by acting as “a reflected cord.” These services are inconsistent with each other and with the anatomy of the parts. If it were fixed so as to draw the bone backward and forward, it could not slide and be of service as a “reflected cord” sufficiently to lower the jaw. To do the latter the anterior belly should be inserted higher up the jaw, while a long unrestricted tendon of the muscle should run through a fixed loop on the lower border of the hyoid bone, which last should also be freed from the styloid ligaments, and be drawn down half way to the sternum every time the jaw opened wide, and proportionally for less opening. In respect to the united action of both bellies drawing the head backward, it is only necessary to say that the origin of the digastric is partly in front of a line drawn across just behind the condyles of the occipital bone; it could not, therefore, draw the head back appre- ciably even if its insertion were directly under its origin. It is con- sequently a mistake to suppose it can do so when its direction forward is so nearly horizontal. In fact this muscle is the great agent in draw- ing the head forward. The posterior belly slants down to the hyoid bone, but the anterior is nearly horizontal in its course, and when the muscle acts it tends to the line of its attachments by drawing or endeavoring to draw the hyoid bone upward, unless the jaw is much depressed, when, as the muscle is straight, or nearly so, it has no power to raise the hyoid bone. But in several important services the digastric acts in concert with the omo-hyoid. In this way the muscles passing from the hyoid bone to the front of the jaw, including the anterior belly of the digastric, are as effectually antagonized as if a powerful muscle passed from each side of the hyoid bone to the opposite cervical vertebrae, with the advantage of greater length of muscle to contract, and easier adaptation to the movements of the