MAN. 



15 



is made up of a head, trunk, and extremities. The head, which 

 includes the skull and the face, is the most important pait of the 

 whole structure. Several wide, thin, arched hones, united by 

 sutures, form the large bony cavity called the skull, which contains 

 the brain, and through all opening in its lower part the spinal 

 marrow passes from the brain to the backbone. The organs of 

 hearing, sight, smell, and taste, which make up the general shape, 

 and constitute the features of the countenance, have for their basis 

 a system of bones, not easily described, and united by sutures. 



The backbone supports the head, which can make many 

 motions upon it, while it is also the main support of the trunk 

 of the body. It is composed of twenty-four distinct vertebrae, 

 placed one above the other, in the form of a pillar or column. 

 The body of each vertebra is a solid, cylindrical piece of bone, 

 united firmly by strong, elastic cartilages, to those above and 

 below it, while behind, and on each side, are projections of bone, 

 styled pi'ocesses, so arched over and connected together, as to form 

 a canal from one end of the vertebral column to the other. The 

 spinal nerve or marrow passes through this canal, and by means 

 of holes between the vertebrae, branches of it are distributed to 

 the various parts of the body. The neck has seven vertebrae, 

 the back twelve, and the loins five j known respectively as the 

 cervical, dorsal, and lumbar vertebrae ; and they increase in size 

 from above downward — the lumbar vertebrae being as much 

 larger, thicker, and stronger than those of the back, as these sur- 

 pass in the same respects those of the neck. 



On each side of the dorsal vertebrae are affixed twelve ribs, 

 which arching over forwards, are united to the breaat-bone by 

 cartilage oi: gristle, and thus form the cavity of the thorax, or 

 chest, which contains the lungs and heart. A muscular mem- 

 brane, called the diaphragm or midrifl^, forms the lower termination 

 of the thoracic cavity, and, extending from the edges of the lower 

 ribs, it stretches across the backbone in such manner as to form a 

 division wall between the chest and the abdomen, immediately 

 below. The abdomen is the cavity usually called the belly, and 

 contains the stomach, liver, spleen, caul, intestines, kidney, etc. 



