82 OSTEOLOGY. 



The table represents the number of bones distinct and separable during adult 

 life : 



Single Bones. Pairs. Total. 



The vertebral column . 26 ... 26 



The skull ... 6 8 22 



Axial skeleton . . The sternum . . 1 ... 1 



The ribs . . .... 12 24 



The hyoid bone . . 1 ... 1 



f The upper limbs . 32 64 



Appendicular skeleton ( The 1( ^ er limbs 31 62 



The ossicles of the ear . . . .... 3 6 



~34 ~86 1J06 



Bones are often classified according to their shape. Thus, long bones, that is to 

 say, bones of elongated cylindrical form, are more or less characteristic of the limbs. 

 Broad or flat bones are plate-like, and serve as protective coverings to the structures 

 they overlie ; the bones of the cranial vault display this particular form. Other 

 bones, such as the carpus and tarsus, are termed short bones ; whilst the bones of the 

 cranial base, the face, and the vertebrae, are frequently referred to as irregular bones. 



Various descriptive terms are applied to the prominences commonly met with 

 on a bone, such as tuberosity, eminence, protuberance, process, tubercle, spine, 

 ridge, crest, and line. These may be articular in their nature, or may serve as 

 points or lines of muscular and ligamentous attachment. The surface of the bone 

 may be excavated into pits, depressions, fovece, fossce, cavities, furrows, grooves, and 

 notches. These may be articular or non-articular, the latter serving for the recep- 

 tion of organs, tendons, ligaments, vessels, and nerves. In some instances the 

 substance of the bone is hollowed out to form an air space, sinus, or antrum. 

 Bones are traversed by foramina and canals ; these may be for the entrance and exit 

 of nutrient vessels, or for the transmission of vessels and nerves from one region to 

 another. A cleft, hiatus, or fissure serves the same purpose ; channels of this kind 

 are usually placed in the line of a suture, or correspond to the line of fusion of the 

 primitive portions of the bone which they pierce. 



Composition of Bone. Bone is composed of a combination of organic and 

 inorganic substances in about the proportion of one to two. 



Organic matter (Fat, etc., Collagen) . . . 31 '04 



Mineral matter 



Calcic phosphate . . . . 58-23' 



Calcic carbonate . . . . 7 '3 2 



Calcic fluoride . . . 1-41 V 68'97 



Magnesic phosphate . . . 1'32 



Sodic chloride '69 



100-00 



The animal matter may be removed by boiling or charring. According to the 

 completeness with which the fibrous elements have been withdrawn, so the brittle- 

 ness of the bone increases. When subjected to high temperatures the earthy 

 matter alone remains. By soaking a bone in acid the salts may be dissolved out, 

 leaving only the organic part. The shape of the bone is still retained, but the 

 organic substance which is left is soft, and it can be bent about in any direction. 

 The toughness and elasticity of bone depends therefore on its organic constituents, 

 whilst its hardness is due to its mineral matter. 



Bone may be examined either in the fresh or dry condition. In the former 

 state it retains all its organic parts, which include the fibrous tissue in and around 

 it, the blood-vessels and their contents, together with the cellular elements found 

 within the substance of the bone itself, and the marrow which occupies the lacunar 

 spaces and marrow cavity. In the dried or macerated bone most of these have 

 disappeared, though a considerable portion of the organic matter still remains, 

 even in bones of great antiquity and in a more or less fossil condition. Con- 

 sidering its nature and the amount of material employed, bone possesses a remark- 

 able strength, equal to nearly twice that of oak, whilst it is capable of resisting a 



