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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1895 Excerpt: ...large size, but the area of its origin is greatly extended (fig. 50, jo) and the axis of its fibers has become more nearly horizontal than vertical (fig. 54, a to zy). Its origin occupies the outer and inferior surface (and probably most of the inner surface also) of the horizontal part of the zygomatic arch for F!g. 51.--Macrogeomys ilulichoccphahig. Via. 53.--Platygeomys gymnurus. Posterior part of cranium from above, showing relations of mandible in place. a Angular process of mandible. fr Frontal. cp Coronoid process of mandible. pa Parietal. ic Incisor capsule (covering root of lower so Supraoecipital. incisor). sq Sqnamosal. ip Interparietal. zy Zygoma. its entire length, its anterior end being in front of the plane of the orbit. The action of this part of the masseter has drawn the zygomatic arch far outward and has pulled the anterior angle downward until the latter is further from the plane of the top of the skull than the posterior end of the arch. The angle is thus drawn down until it reaches four-fifths of the way from the plane of the top of the skull to the plane of the molar alveolus, overreaching and overarching the maxillary or principal part of the masseter muscle, which operates beneath it (fig. 50, which should be contrasted with fig. 49 of Mucrogeomys dolichocejjhalus). The insertion of the muscle has produced an equally extraordinary effect upou the shape of the under jaw. The sides of the jaw are not only spread widely apart in conformity with the great breadth of the skull, but in addition the fibers of the niasseter that are inserted on the angular process have stimulated this process to push out sideways until it reaches off' like a long arm at nearly a right angle to the axis of the. skull (figs. 53 and 54, a). The lengthening of ...