12 GENERAL PBINCIPLES APPLICABLE TO 



The diarthrodial eminences are voluminous and smooth, and in a fresh 

 state are covered with cartilage. They are named heads and condyles : 

 heads, when they describe the segment of a sphere (head of the femur, head 

 of the humerus) ; condyles, when they represent the segment of an oval 

 figure, cut parallel to its large axis (condyles of the femur.) 



The non-articular eminences receive various names. If they are volumi- 

 nous and much detached from the bone, they are called processes or apophyses. 

 Apophyses receive qualiflcatives derived from the analogies perceived between 

 them and known objects. (Examples : — the styloid, clinoid, coronoid and 

 coracoid processes.) The appellations of protuberances and tuberosities 

 are given to non-articular eminences when they are large and round, and 

 but slightly prominent. Lastly, they are named lines, crests, and ridges, 

 when they are narrow and very long. 



Cavities. — The cavities of bones have also bsen divided into articular and 

 non-articular cavities. 



The first correspond to the eminences of the same name in the bony 

 joints. They take the designation of cotyloid cavities when they are deeply 

 excavated, like a basin or the cup of an acorn (the glenoid cavity of the 

 scapula, and the cotyloid cavity of the coxa). 



The non-articular cavities serve either for ligamentous or muscular 

 implantation, or for the passage of vessels, nerves, tendons, etc. 



They are termed channels or furrows, when they are wide, deep, and 

 smooth ; grooves, when they are long, narrow, and even at the bottom ; 

 fissures, when they are narrow and rough. Digital impressions is the name 

 given to those excavations in bones which look as if produced by the 

 pressure of the finger. The fosses, sinuses, cells, and notches are also non- 

 articular cavities of bones. The sinuses and cells are formed by open 

 spaces in the interior of bones; notches, by cavities excavated on their 

 margins. 



When a cavity passes quite through a bone it is termed a foramen. If 

 this foramen offers a certain length, it is then designated a conduit or canal. 

 Fissures are long, narrow foramina; hiatus is the term applied to wide 

 openings with iiTegular outlines. 



Eegions of the Bones. — When it is desired to describe the eminences 

 and external cavities of a bone, it is essential not to notice them, as it were, 

 by chance— passing indifferently from one to another. In order to avoid 

 the difficulties which would result from the application of such an irrational 

 system, it is convenient to divide the bone to be described into several 

 regions, in which are examined, one after another, all the external peculiari- 

 ties that may offer. 



The following is the course to pursue in order to establish the regions 

 of a long, a flat, and a short bone. 



(a) A long bone is always divided into three parts : a body and two 

 extremities. The body, middle part, or diaphysis, is the narrowest poi-tion of 

 the bone. It represents a geometrical solid, approaching more or less the 

 figure of a very elongated prism. In a long bone, therefore, it is necessary 

 to study as many faces, angles, or borders, as the prism it represents may 

 offer. 



With regard to the extremities, or epiphyses, these are more or less con- 

 siderable enlargements, showing articular surfaces, as well as surfaces 

 intended for muscular or ligamentous insertion. 



(6) A flat bone must necessarily have two faces, as well as borders and 

 angles. 



