GENERAL PBINOIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 15 



Apophyses receive qualificatives derived from the analogies perceived between 

 them and known objects (examples : the styloid, clinoid, coronoid, and coracoid 

 processes). The appellations of protuberances and hiherosities are given to non- 

 articular eminences when they are large and round, and slightly detached. 

 Lastly, they are named lines, crests, and ridges, when they are narrow and 

 very long. 



The processes are sometimes epiphysary in early life, and formed by a special 

 nucleus. 



B. Cavities. — The cavities of bones have also been divided into articular, 

 diarthrodial or synarthrodia! , and non-articular cavities. 



a. The diarthrodial cavities correspond to the eminences of the same name in 

 the bony joints. They take the designation of glenoid cavities when they are 

 oval and shallow, and cotyloid cavities when they are deeply excavated, like a 

 basin or the cup of an acorn (examples : the glenoid cavity of the scapula, and the 

 cotyloid cavity of the coxa). The synarthrodial cavities fit into the dentations 

 opposed to them. 



b. The non-articular cavities serve either for hgamentous or muscular 

 insertion, 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 smooth at the bottom ; and fissures, 

 when they are narrow and rugged. Digitcd impi'essions is the name given to 

 those excavations in bones which look as if produced by the pressure of the 

 finger. The fossce, 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 has a certain length, it is designated a conduit or canal. Fissures are 

 long, narrow openings ; hiatus is the term applied to a wide opening with an 

 irregular outline. 



In order to aid the memory, the external peculiarities of bones are grouped 

 in the following synoptical table : — 



i Non-Articulars 



( Synarthrodials . Dentations. 

 JDiarthrodials . ( gf^^^^s. 



I Styloids. 

 Coracoids. 

 Mastoids. 

 1 1 uoerosiiies. 



Lines. 

 ^Crests. 



Internal Conformation of Bones. 



Sections made in various directions through the substance of bones, show 

 that their internal conformation varies, according as they belong to the category 

 of long, flat, or short bones The diaphysis of long bones is hollowed out into a 

 large fusiform cavity — the medullary canal. This' canal is absent in the flat and 

 short bones, and is replaced by irregular cavities which communicate with each 

 other, called medullary spaces. Its walls are formed by a very dense bony tissue, 



