Ixxxviii 



sufficient magnitude and strength are attained without undue increase of 

 weight. 2. Tabular or flat bones, like the scapula, the ilium, the ribs, the 

 lower jaw, and the bones forming the roof and sides of the skull. Many of 

 these contribute to form the walls of cavities. 3. Short bones, often also 

 called round bones, though most of them rather are angular ; the wrist and 

 tarsus afford examples of these. 4. Irregular or mixed bones, which would, 

 perhaps, be better named " complex : " such as cannot be entirely referred 

 to any of the foregoing classes. These are mostly situated in the median 

 plane, and have a complex but symmetrical figure ; the vertebrae may be 

 taken as instances of them. 



The surfaces of bones present various eminences, depressions, and other 

 marks ; and, to designate these in descriptive osteology, certain general 

 terms are employed, of which the following are those most commonly in use. 



1. Eminences. To any prominent elevation jutting out from the surface 

 of a bone the term " process " or " apophysis" is applied. It often happens 

 that such a process is originally ossified separately from the rest of the bone, 

 and remains long unconnected with the main body (by osseous union at 

 least); in this condition it is named an "epiphysis." In many bones, 

 considerable portions at the extremities or most prominent parts are 

 originally ossified separately as epiphyses. This is the case with the 

 ends of the long bones, and in this instance the shaft is named the 

 " diaphysis." 



Processes or apophyses are further designated according to their different 

 forms. A slender, sharp, or pointed eminence is named a " spine " or 

 " spinous process ; " a tubercle, on the other hand, is a blunt prominence ; 

 a " tuberosity " (tuber) is broader in proportion to its elevation, and has a 

 rough uneven surface. The term "crest" is usually applied to the 

 prominent border of a bone, or to an elevation running some way along its 

 surface ; but the latter is more commonly denominated a " line " or 

 "ridge." A "head" (caput, capitulum, or capitellum) is a rounded 

 process, supported on a narrower part named its neck (cervix). A " cori- 

 dyle " has been defined to be an eminence bearing a flattened articular 

 surface ; but this term has been very variously applied by anatomists both 

 ancient and modern. 



2. Cavities and depressions of bones. An aperture or perforation in the 

 substance of a bone is named a " foramen," A passage or perforation often 

 runs for some way in the bone, and then it is termed a " canal " or 

 "meatus." On the other hand, it may assume the form of a "fissure," 

 and is named accordingly. A "fossa" is an open excavation or depression 

 on the surface of a bone, or of a part of the skeleton formed by several 

 bones. A fossa may form part of a joint, and be adapted to receive the 

 prominent part of a neighbouring bone; it is then said to be "glenoid," 

 when shallow ; but a deep excavation, of which the socket for the head of 

 the thigh-bone is an example, is named a " cotyloid" cavity. The meanings 

 of the terms "notch" (incisura), and "groove," or "furrow" (sulcus), are 

 sufficiently plain. " Sinus " and "antrum"are names applied to certain 

 large cavities situated within the bones of the head and opening into 

 the nose. 



Physical properties of lone. Bone has a white colour, with a pink and 

 slightly bluish tint in the living body. Its hardness is well known, but it 

 also possesses a certain degree of toughness and elasticity ; the last pro- 

 perty is peculiarly well marked in the ribs. Its specific gravity is from 1'87 

 to 1-97. 



