To sum up, if we fancy the human being in the position of the quadruped, the scapula will have its surfaces almost parallel to the ground (Fig. 10); while in quadrupeds, the surfaces are situated in a plane which is almost perpendicular to the ground (Fig. 11). This position of the scapula in an almost vertical plane is designed to give the necessary point of support to the osseous columns that form the skeleton of the other portions of the anterior limbs. Because of this position of the scapula (Figs. 12 and 13), the spinal border is superior, the cervical, anterior, and the axillary, posterior. In direct contrast to what obtains in the human scapula, the spinal border is the shortest of the three; except in the bat, and the majority of the cetaceans. [Illustration: FIG. 10.--SITUATION AND DIRECTION OF THE SCAPULA IN THE HUMAN BEING, THE TRUNK BEING HORIZONTAL, AS IN QUADRUPEDS. VERTICAL AND TRANSVERSE SECTION OF THE THORAX (DIAGRAMMATIC FIGURE). 1, Contour of the thorax; 2, 2, the scapula.] [Illustration: FIG. 11.--POSITION AND DIRECTION OF THE SCAPULA IN QUADRUPEDS. VERTICAL AND TRANSVERSE SECTION OF THE THORAX (DIAGRAMMATIC FIGURE). 1, Contour of the thorax; 2, 2, the scapula.] 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. 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). [Illustration: FIG. 12.--LEFT SCAPULA OF THE HUMAN BEING, POSTERIOR SURFACE, PLACED IN THE POSITION WHICH IT WOULD OCCUPY IN THE SKELETON OF A QUADRUPED. 1, Cervical border; 2, spinal border; 3, axillary border; 4, supraspinous fossa; 5, subspinous fossa; 6, scapular spine; 7, glenoid cavity; 8, coracoid process; 9, acromion process.] [Illustration: FIG. 13.--LEFT SCAPULA OF A HORSE: EXTERNAL SURFACE. 1, Cervical border; 2, spinal border--the scapula here represented, being from a hoofed animal, has a cartilage of extension attached to its spinal border; 3, axillary border; 4, supraspinous fossa; 5, subspinous fossa; 6, spine of the scapula; 7, glenoid cavity; 8, coracoid process. The scapula of the horse has no acromion process, but it is easy, if we compare the human scapula, to judge of the position which this process would occupy if it were present.]