A manual of dental anatomy, human and comparative / by Charles S. Tomes ; edited by H.W. Marett Tims and A. Hopewell-Smith.

  • Tomes, Charles S. (Charles Sissmore), Sir, 1846-1928.
Date:
1914
Catalogue details

Licence: In copyright

Credit: A manual of dental anatomy, human and comparative / by Charles S. Tomes ; edited by H.W. Marett Tims and A. Hopewell-Smith. 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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    temporal, and internal pterygoid) muscles close the jaws, only slight and weak ones (digastric, mylohyoid, and geniohyoid, aided perhaps by the platysma) open them, and the weight of the mandible is enough per se to open the mouth. The position of repose is neither complete closure nor opening of the jaws; in persons with nasal obstruction the habitual position is one with the mouth somewhat more widely open, owing to the difficulty of breathing through the nose, a fact which may cause an irregularity in the disposition of the teeth. Just as the muscles of mastication vary in their relative development in accordance with the food to be dealt with, so also do the salivary glands. As a rule herbivorous creatures have large parotid glands; that is to say, those creatures which deal with the driest food and masticate it the most, have this gland largely developed. For instance, it is very large in the ox and other ruminants; in herbivorous marsupials it is larger, and in the carnivorous section smaller, than the submaxillary gland. When an especially viscid fluid is required, as, for example, that which lubricates the tongue of an ant-eater, it is furnished by exceedingly large submaxillary glands. The form of the glenoid cavity also bears an intimate relation to the type of dentition of the animal and the nature and extent of the movement of its jaws. Thus in a child it is nearly flat, with no well-marked sur- rounding elevations; its axis is transverse, and little rotary motion is made use of. In the adult it is deeply sunk ; the axis of the condyle is oblique, and rotary movements are largely made use of in triturating food. In the Felidce, it is strictly transverse; their teeth, adapted for slicing but not grinding, would gain nothing by lateral motion, which is rendered quite impossible by the manner in which the long transverse condyles are locked into the glenoid cavity by strong processes in front and behind. Curiously enough, the interarticular cartilage is present, but as the condyle never moves forward, the cartilage is not attached to the external pterygoid muscle. In the Ungulata the condyle is rounded, the ascending ramus long, the pterygoid muscles large, and the glenoid cavity shallow. In the whale, which of course does not