ANDRONOMY. 407 



the sternum, and the ossa innominata. The vertebrae, or joints, 

 which together form the vertebral column, called the spine, or back 

 bone, are twenty-four in number. The ribs, extending from the 

 spine around the sides, are twelve in number on each side ; of which 

 the upper seven are called true ribs ; and the others, being shorter, 

 are called false ribs. The sternum, or breast bone, generally con- 

 sisting of three pieces, extends vertically along the breast; and is 

 connected by cartilages, with the ribs on each side. The ossa inno- 

 minata, are the hip-bones; between which is the sacrum, a bone 

 supporting the spine, and terminated by the coccyx, of a conical 

 form. 



The upper, or atlantal extremities, consist of the clavicula, or 

 collar bone, in front, serving to brace back the scapula, or shoulder 

 blade ; which latter supports the os humeri, or bone of the upper 

 arm ; and to this are attached the two bones of the lower arm, the 

 radius and ulna; the former being on the side towards the thumb. 

 Eight bones of the carpus, or wrist ; five of the metacarpus, or 

 palm of the hand ; twelve bones of the fingers ; and two of the 

 thumb ; complete the list of bones in the upper extremities ; thirty- 

 two on each side. The lower or sacral extremities, consist of the 

 os femoris, or thigh bone ; the patella, or knee pan ; the tibia, or 

 large bone of the leg ; the fibula, or small hinder bone of the leg ; 

 the os calcis, or heel bone ; and six other bones of the tarsus, or 

 instep; five bones of the metatarsus, or body of the foot; and four- 

 teen bones of the toes ; making in all, thirty bones on each side. 

 The bones are covered with a firm membrane, called the periosteum; 

 which receives, where it invests the skull, the name of pericranium : 

 and the joints are lined with cartilage or gristle, to prevent their 

 wearing. They are kept together by strong fibrous ligaments, the 

 study of which is termed Syndesmology ; but of which we have 

 here no room to treat. 



2. Myology, is that division of Anatomy which treats of the 

 muscles. ' These organs are almost entirely composed of fibres, 

 usually of a red color, and placed side by side, but sometimes of 

 considerable thickness ; as shown in the lean part of animal flesh. 

 They are the immediate agents, by means of which all animal motion 

 is produced, whether of mere vitality or of volition. They act, in 

 every case, by contraction ; whether to expel the blood from the 

 heart, or to move a limb : and this contraction, produced probably by 

 the galvanic action of the nerves, is one of the mysteries of animal 

 life. If the brain is compressed, the power of contracting the mus- 

 cles, by volition, ceases ; and life soon becomes extinct. The mus- 

 cles constitute the fleshy part of the body ; and sometimes cross over 

 each other, or interlace ; while, at other times, they pass through 

 loops, like a cord over a pulley, in order to produce the requisite 

 motion. Those which move the limbs, are attached to the bones, 

 mostly near the joints, by means of tendons or sinews ; and those 

 on opposite sides often counterbalance each other's effects. 



The muscles are classed according to the region of the body 

 which they occupy; and they are about 527 in number; of which 

 257 are in pairs, and on opposite sides of the body. To describe 



