In certain animals (in the ungulates [hoofed[6]]—pigs, oxen, sheep, horses) the superior, or spinal, border of the scapula is surmounted by a cartilage called the cartilage of prolongation.
[6] For the definition of the word hoofed, see [p. 37].
Fig. 14.—Vertical and Transverse Section, at the Site of the Shoulders, of the Thorax of the Horse (Diagrammatic Figure).
1, Outline of the thorax at the level of the third dorsal vertebra; 2, 2, scapula; 3, spinal border of the scapula; 4, cartilage of prolongation; 5, contour of the skin.
This is the cause why the border to which it is fixed is so slightly noticeable under the skin in these animals; indeed, in the upper part, the bone and cartilage are not distinguishable in the contour of the corresponding region of the back; being applied to the lateral surfaces of the spinous processes, the prominence formed by the extremities of which is directly continuous with the plane of the scapula ([Fig. 16]).
Fig. 15.—Vertical and Transverse Section, at the Plane of the Shoulders, of the Thorax of a Dog (Diagrammatic Figure).