THE ARMY HORSE. 21 



carpal bones are joined together, forming the metacarpus) ; 

 two sesamoids^ pulley bones; os sujfraginh^ upper pastern 

 bone ; os corona'^ lower pastern bone ; os pedis, coffin bone, and 

 OS navicularis, shuttle bone. The scapula is extended by means 

 of a thin plate of gristle, called the cartilage of prolongation, 

 Avhich offers additional attachment for the muscles of the body. 



The pelvis is composed of two segments. In each segment 

 are three united,, irregularly shaped, flat bones, namely, ilium, 

 ischium, and pubis (haunch bones). The ischium and pubis 

 bones are also united in pairs, forming the floor of the pelvic 

 cavity occupied by the bladder and rectum. The two ilium 

 bones or branches are triangular in shape. The outer angle in 

 each case is the point of the hip. The two inner angles are 

 close to each other, and together form the point of the croup. 

 Just below this point each branch is attached to the sacrum by 

 ligaments. 



The hind leg is composed of the following bones: Femur, 

 thigh bone; tibia, leg bone; p'bida, accessory leg bone; patella, 

 stifle bone; tarsus, hock (made up of six small bones, named 

 calcaneum, asti^agalus, cuneiform Tnagnum, medium, parvum, 

 and cuboid) ; large metatarsal, cannon bone; two small meta- 

 tarsals, splint bones. Below the cannon, the bones have the 

 same name as in the fore leg. 



JOINTS. 



A joint is a movable union between two or more bones; the 

 bones are separated b}' a soft elastic substance, which varies in 

 structure with the amount of motion. Covering the adjacent 

 surfaces in the joint is a thin and very smooth layer of a pecu- 

 liar kind of cartilage called articular cartilage. A lubricating 

 fluid, synovia, joint oil, is required to reduce the amount of 

 friction ; this fluid is secreted or formed by the synovial mem- 

 brane and the latter is confined and protected by the capsular 

 ligament which completely surrounds the joint. 



The joints of the fore leg are as follows: Shoidder joint, 

 formed by the loAver end of the scapula and the head of the 

 humerus; elbow joint, by the radius, ulna, and humerus; knee- 

 joint, by the radius, seven small bones (carpals), and the upper 

 end of the metacarpals; fetlock joint, by the large caunon, up- 

 per pastern bone, and the two sesamoids; pastern joint, by the 

 upper and lower pastern l)ones; co-ffin joint, by the lower 

 pastern, coffin bone, and shuttle bone. 



