THE SKELETAL SYSTEM 



41 



ossification. The upper surface is triangular in shape, narrow 



in front. The lateral surfaces present seven articular cavities 



for the cartilages of the true ribs. 



The inferior border is convex, I 



keel-like, and may be distinctly \ 



felt in the living animal. Both 



extremities are cartilaginous. 



BONES OF THE APPENDICULAR 

 SKELETON 



-Humerus 



Ulna 



Radius 



The appendicular skeleton com- \ 

 prises the bones of the thoracic 

 and pelvic limbs. 



A. The bones of the thoracic or 

 fore limb, named from above 

 downward, are the scapula or 

 shoulder-blade, the humerus or 

 arm, the radius and ulna or fore- 

 arm, the carpus or knee, the meta- 

 carpus consisting of the cannon 

 and two splint bones, the first ' 

 phalanx or large pastern, the 

 second phalanx or small pastern, 

 the third phalanx or coffin bone, 

 the proximal pair of sesamoids, | 

 and the distal sesamoid or 

 navicular bone (Fig. 6). 



The scapula is located on the 

 anterolateral surface of the thorax. \ 

 In the horse it is connected to the | 

 axial skeleton by muscles only. 

 It is directed obliquely downward 

 and forward. The scapula is a 

 flat bone, triangular in shape, |; 

 presenting for description two||g 

 surfaces, three borders, and three 

 angles. The external surface is 

 divided into two unequal parts 

 by the spine, a prominent ridge 

 running lengthwise the bone. The narrow fossa in front 

 of the spine is named theuupraspinous fossa and the one posterior 



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K ■ 



Scapula 



■ 



Carpus 



' Metacarpus 



Sesamoid 

 First phalanx 

 Second phalanx 

 Third phalanx 



Fig. 6. — Skeleton of left fore limb 

 of horse (lateral view). 



