HORSESHOEING. 17 



are therefore called true ribs, while the last ten pairs are only 

 indirectly attached to the sternum, and are consequently called 

 false ribs. The sternum (8) lies between the forelegs, and helps 

 to form the floor of the chest cavity. The space enclosed by the 

 bones of the thorax is called the thoracic, pulmonary, or chest 

 cavity, and contains the heart and lungs. The bones of the pelvis 

 form a complete circle or girdle. The upper part, called the 

 ilium (9'), articulates on its inner side with the sacrum (5), 

 while its outer side is prolonged to form a prominent angle, 

 which is the support of the hip, and is called the " point of the 

 hip." The posterior part of the pelvis is called the ischium 

 (9"), and that part lying between the ilium and the ischium and 

 forming part of the floor of the pelvis is called the pubis. 



The space between the thorax and the pelvis, bounded above 

 by the lumbar vertebrae and shut in below and on the sides by 

 the skin and muscular walls of the belly (abdomen), is called 

 the abdominal cavity. This cavity opens directly into the pel- 

 vic cavity, and contains the stomach, intestines, liver, spleen, 

 pancreas, kidneys, and a part of the generative organs. The 

 thoracic and abdominal cavities are separated by a muscular 

 partition, the diaphragm. 



The bones of the limbs may be Hkened to columns, upon 

 which the body rests ; they articulate with one another at various 

 angles, are tubular in structure, and strong. 



The bones of the fore-limbs do not articulate directly with the 

 bones of the trunk, but are attached to the body by means of the 

 skin and muscles. From above to below we distinguish the 

 following bones : 



1. The scapula, or shoulder-blade (10), a flat, triangular bone, 

 prolonged at its upper border by a flat, very elastic cartilage, 

 called the scapular cartilage. At its lower end the scapula 

 articulates with — 



2. The upper end of the humerus (11), forming the shoulder- 

 joint (scapulo-humeral articulation). The humerus articulates 



at its lower end with — 



2 



