Fig. 43.—The Left Iliac Bone of the Human Being: External Surface, placed in the Position which it would occupy in the Skeleton Of a Quadruped.
1, Cotyloid cavity; 2, ilium; 3, iliac crest; 4, anterior iliac crest; 5, posterior iliac spine; 6, pubis; 7, tuberosity of the ischium; 8, obturator foramen; 9, ischiadic spine.
The bones which form the skeleton of the pelvis of quadrupeds are proportionally more elongated and less massive than those of the human pelvis ([Figs. 43] and [44]).
Fig. 44.—Left Iliac Bone of A Quadruped (Horse): External Surface.
1, Cotyloid cavity; 2, ilium, external iliac fossa (directed upward in the horse); 3, iliac crest; 4, anterior iliac spine (directed inwards in the horse, it is the angle of the haunch); 5, posterior iliac spine (directed inwards in the horse; it is the angle of the haunch); 6, pubis; 7, tuberosity of the ischium; 8, obturator foramen; 9, ischiadic spine, or subcotyloid foramen.
We find, on the external surface of the iliac bone, the cotyloid cavity, whose border is interrupted by the cotyloid notch; a deep notch which looks downwards.
In front of this cavity is the ilium. This portion, narrow in the part which is next the cavity, is directed forwards and upwards, expanding more and more as it passes upwards. It presents an external or superior surface (external in some animals, superior in others), which recalls the external iliac fossa; and an internal or inferior surface, at the superior part of which is found the auricular surface for articulation with the sacrum.
The anterior border of the ilium is rough; this is the iliac crest, at the extremities of which we find, below or outside, a prominence which corresponds to the anterior superior iliac spine of man; and internally another projection which corresponds to the posterior iliac spine.