36 



GENERAL ANA TOM Y OF THE SKELETON 



bones belonging to this class are the clavicle, humerus, radius, ulna, femur, tibia, 

 fibula, metacarpal and metatarsal bones, and the phalanges. 



J Short Bones. Where a part of the skeleton is intended for strength and 

 compactness, and its motion is at the same time slight and limited, it is divided 

 into a number of small bones united by ligaments, and the separate bones are 



short and compressed, such as the bones of 

 the carpus and tarsus. These consist of can- 

 cellous tissue covered by a thin crust of com- 

 pact substance. The patellae also, together 

 with the other sesamoid bones, are by some 

 regarded as short bones. 



Flat Bones. Where the principal re- 

 quirement is either extensive protection or 

 the provision of broad surfaces for the at- 

 tachment of muscles, we find the osseous 

 structure expanded into broad, flat plates, 

 as is seen in the bones of the skull and the 

 scapulae. Flat bones are composed of two 

 thin layers of compact tissue enclosing be- 

 tween them a variable quantity of cancellous 

 tissue. In the cranial bones these layers of 

 compact tissue are familiarly known as the 

 tables of the skull; the outer table is thick 

 and tough; the inner table is thinner, denser, 

 and more brittle, and hence is termed the 

 vitreous table. The interveningcancellous 

 tissue is called the diploe. TEe Ila/p bones 

 are: the occipital, parietal, frontaTTnasal, lacri- 

 mal, vomer, scapula, os innominatum, sternum, 

 ribs, and, according to some, the patella. 



Irregular Bones. The irregular or mixed 

 bones are such as, from their peculiar form, 

 cannot be grouped under either of the pre- 

 ceding heads. Their structure is similar to 

 that of other bones, consisting of a layer of 

 compact tissue externally and of sponj 

 cancellous tissue within. The 

 bones are: the vertebras, sacrum, coccyx, 

 temporal, sphenoid, ethmoid, malar, maxilla, 

 mandible, palate, turbinated, and hyoid. 



Surfaces of Bones. If the surface of 

 any bone is examined, certain eminences 

 and depressions are seen, to which descrip- 

 tive anatomists have given the following 

 names. 



These eminences and depressions are of 

 two kinds: articular and nonarticular. Well- 

 marked examples of articular eminences are 



found in the heads of the hnnienis and femur, and of articular depressions in the 

 U'lenoid cavity of the scapula and the acetabulum. Xonarticular eminences are 

 designated according to their form. Thus a broad, rough, uneven elevation is 

 called a | tuberosiffi ; a small, rough prominence, a tubercle; a sharp, slender, pointed 

 eminence, a spine; a narrow, rough elevation, running some way along the surface, 

 a ridge, line, or crest. 



FIG. 1. General view of the human skeleton. 



