. The anatomical record. Anatomy; Anatomy. TEMPORO-MANDIBULAR ARTICULATION 463 plane, is thus parallel to the resultant of the combined pull of the two external pterygoids, the main muscles utilized in open- ing the mouth. Examining the condyle of the diseased joint bj^ an imaginary coronal section its two surfaces are seen to slant as follows: the slope running laterally from the ridge at its summit makes an angle of about twenty" degrees with the horizontal, while the. Fig. 1 Drawing of condyles of mandible. The upper figures show the con- dyles as seen from behind; the line below the u
. The anatomical record. Anatomy; Anatomy. TEMPORO-MANDIBULAR ARTICULATION 463 plane, is thus parallel to the resultant of the combined pull of the two external pterygoids, the main muscles utilized in open- ing the mouth. Examining the condyle of the diseased joint bj^ an imaginary coronal section its two surfaces are seen to slant as follows: the slope running laterally from the ridge at its summit makes an angle of about twenty" degrees with the horizontal, while the. Fig. 1 Drawing of condyles of mandible. The upper figures show the con- dyles as seen from behind; the line below the upper part of the drawing gives the edge of the articulating surface. The lower figures sliow a view of the con- dyles from above. In each case the right hand figure represents a view of the pathological right side, showing its enlarged and altered articulating surface. The dotted lines show the approximate number of degrees of slope from the hori- zontal of each side of the joint surface. surface running mesially from the ridge makes an angle of about forty degrees—being about twice as steep (fig. 1). The reason for this appears when we examine the planes in which the closing muscles act. The temporal muscle pulls practically vertically, not tending to dislocate the condyle either mesially or laterally. The masseter pulls laterally at an angle of twenty degrees from the vertical, tending to pull the condyle outward, the internal pterygoid tends to pull the condyle inward, as it acts at an angle THE ANATO^^CAL RECORD, VOL. 9, NO. 6. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bardeen, Charles Russell, 1871-1935, ed; Boyden, Edward A. (Edward Allen), 1886-1976; Bremer, John Lewis, 1874- ed; Hardesty, Irving, b. 1866, ed; American Association of Anatomists; American Society of Zoologists; Wistar Institute
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