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3. Dorsal Vertebrae or Back-Bone.—Dorsal bones are eighteen in number. The chief point of interest about them are the height of the spines on the upper surface of the bones. These large spines form the withers of the horse, as will be noticed in the skeleton. On either side of these bones the ribs are attached, 18 pairs corresponding with the number of bones in this region.

4. Lumbar Vertebrae (or the bones which form the skeleton of the loins). These bones are six in number, and they are situated immediately above the kidneys.

5. Sacral Vertebrae or Rump Bones.—There are five of these bones in the young horse, but in the adult they unite as a single bone, somewhat triangular-shape. These are situated between the upper hip bones and help to form the rump. Beneath these bones the bladder is situated.

6. Coccygeal Vertebrae or Tail Bones.—These are 18 to 20 in number. There is no complete canal, like in the previous vertebraes, for enclosure of the spinal cord.

7. Pelvic or Hip Bones.—The pelvic bones are flat, but somewhat irregularly-shaped, and they form the sides, floor, and part of the roof of the pelvic cavity. Above they are connected with the sacrum, and below united to each other, in the adult, by ossification (union of bone). In the young animal, as above stated, and especially in the foetus, each side consists of three parts, which retain their names of ilium, ischium, and pubis, even after union by ossification. They all three meet in the acetabulum, or articular cavity for the femur or hip bone.