20 OSTEOLOGY. 



internal surface faces the median plane of the body, the anterior 

 surface the anterior vertical, the posterior surface the posterior 

 vertical plane, while the superior and inferior surfaces are those 

 facing their respective superior and inferior planes. This imagin- 

 ary index may be applied to any region, as well as to the entire 

 body. 



Modifications of these terms are used when it is requisite to 

 point out the precise situation of a structure. For example, take 

 the anterior limb, and suppose it encompassed by the planes ut 

 supra. If we wish to describe the situation of any object on the 

 upper part of its lateral region, the term supero-lateral would be 

 used ; if the object were situated at the lower lateral part, then 

 infero-lateral. Similar modifications of terms are, of course, 

 applicable to the anterior and posterior surfaces. Supero-anterior 

 implies the superior part of the anterior region, and antero- 

 superior the anterior part of the superior region. For description, 

 structures are frequently divided into two or more parts ; thus 

 we allude to the superior, middle, or inferior third of an object. 

 The end of a structure which is nearest to the vertebral column 

 is often termed the proximal, while the remote end is termed 

 the distal extremity. 



DIVISION OF THE SKELETON. 



The limbs, with their media of attachment, form the 

 APPENDICULAR SKELETON ; while the remaining portion of the 

 structure, consisting of the skull, vertebras, ribs, and breast-bone, 

 is called the AXIAL SKELETON, fty many authorities the skull 

 is regarded as being formed of a number of modified vertebrae, 

 while the ribs and breast-bone, or sternum, are considered parts 

 of complete vertebral segments. Taking this view, the term 

 axial skeleton would be synonymous with vertebral column. In 

 this work we first describe the axial skeleton, dividing it into 

 the vertebral column and the skull, afterwards treating of the 

 appendicular skeleton. The following Table will exhibit this 

 division : 



Axial Skeleton. 



f Cranium. 

 Sklll! ' Face. 



