100 THE SKELETON 



and serves to keep the first of these bones in its natural position, 

 and to prevent the shoulder from falling too far forward. 



44. The arm is firmed of a single bone called the humerus. 

 This bone is of a cylindrical form and has a swelling at its supe- 

 rior extremity called the head of the humerus which articulates 

 with the glenoid cavity of the scnpula. Its inferior extremity is 

 enlarged transversely and resembles a pully upon which moves 



he fore arm. 



45. The fore-arm is formed by the union of two bones which 

 are; on the inner side, the cuhitv* or n/na, and on the outside, 

 (the side on which the thumb is placed) the radi'is. These bones 

 are joined to the humerus by their superior extremities and to the 

 hand by their inferior extremities. 



46. The hand in man is divided into three regions ; the carpus, 

 the metucarpns and fingers; the carpus or wrist, is composed of 

 eight small bones, ranged in two rows and united to each other by 

 fibrous threads which preserve their mutual relations and permit 

 them to move a little upon each other, by aid of the smooth sur- 

 faces by which they are in contact. 



47. The metacarpus is composed of five bones which may be 

 regarded as the origin of the fingers. They are placed parallel, 

 one along side of the other; their superior extremities articulate 

 with the bones of the carpus and their inferior extremities with 

 the fingers. 



48. The fingers are composed of small bones articulated one at 

 the extremity of the other, and called phalanges. Except the 

 thumb which has but two, each finger has three of these bones. 



49. The iitfeiior extremities are formed nearly in the same 

 manner as the superior; the hip represents the shoulder, the 

 thigh the arm; the leg the fore-arm, and the foot the hand. 



50. The hip or haunch serves to support the abdominal mem- 

 ber or lower extremity, as the shoulder sustains the thoracic 

 member It is formed on each side by a very large, and very 

 strong bone, the ilium. These bones are united together in front, 

 and behind they articulate with the sacrum, so as to form in 

 conjunction with it at the bottom of the belly, a sort of bony 

 belt called the pdvis or hasin. In infancy, we find that the ilium 

 bone consists of three separate portions one of which resembles 



44. What is the character of the bone of the arm ' 

 4-5. How is the fore arm formed? 



46. How is the hand divided ? 



47. What is the metacarpus? 



48. How are the fingers composed ? 



4!). How are the inferior extremities formed ? 



50. What forms the hip ? What is the condition of the pelvis in infancy * 



