. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 142 PELVIS. by the line P c, and the line of gravity of the trunk, ca, and is doubtless considerably increased by the resisting tension of the an- terior abdominal muscles acting through the extensors of the thigh on the femoral sup- ports in the line c b, b d. In the foregoing dispositions of the pelvic structure, the office fulfilled by the sacrum is so compendious and important as to call for particular attention to the shape and position of that bone, and the manner in which it is articulated with the ilia, so as to
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 142 PELVIS. by the line P c, and the line of gravity of the trunk, ca, and is doubtless considerably increased by the resisting tension of the an- terior abdominal muscles acting through the extensors of the thigh on the femoral sup- ports in the line c b, b d. In the foregoing dispositions of the pelvic structure, the office fulfilled by the sacrum is so compendious and important as to call for particular attention to the shape and position of that bone, and the manner in which it is articulated with the ilia, so as to be at once firm and strong as a keystone, yielding as a spring, and moveable as a jointed bone. And we shall find all these requirements beauti- fully provided for. First. The sacrum is wedge-shaped, when viewed at its anterior aspect, narrowing from above downward, especially along the surface immediately between the lower portions of its iliac articular surfaces in the plane b, e (fig. 88. A), which are inclined to each other at an angle varying from 15° to 30°, and aver- aging about 20°. When viewed from above at its base, as in fig. 89. page 144.), it also pre- sents a wedge shape with the base directed ante- rior/^, the lateral masses of the base becoming narrower from before backwards ; so that the Fig. 88. a. 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 Todd, Robert Bentley, 1809-1860. London, Sherwood, Gilbert, and Piper
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