THE VERTEBRAL COLUMN 



29 



The shafts of long bones at the time of birth are mainly cylindrical and free from ridges. 

 The majority of the lines and ridges so conspicuous on the shafts of long bones in adults are due 

 to the ossification of muscle-attachments. The more developed the muscles, the better marked 

 the ridges become. 



The surfaces of bones are variously modified by environing conditions. Pressure at the 

 extremities causes enlargement, and movement renders them smooth. The two causes combined 

 produce an articular surface. When rounded and supported upon a constricted portion of bone, 

 an articular sm-face is termed a head, sometimes a condyle ; when depressed, a glenoid fossa. 

 Blunt, non-articular processes are called tuberosities; smaller ones, tubercles; sharp projections, 

 spines. Slightly elevated ridges of bones are crests; when narrow and pronounced, lines and 



Fig. 32.— The Tibia and Fibula in Section to show the Epiphyses. 



Epiphysis 



Centre of ossification of epiphysis 

 Epiphysial line 



{ 



Shaft of fibula 



Shaft of tibia in section 



Epiphysis of tibia 

 Epiphysis of fibula 



borders. A shallow depression is a fossa; when narrow and deep, a groove; a perforation is 

 usually called a foramen. 



In addition to these, other terms are employed which do not require any explanation, such 

 as canal, notch or incisura, sulcus or furrow, and the like. 



/. THE AXIAL SKELETON 



A. THE VERTEBRAL COLUMN 



The vertebral column [columna vertebralis] consists of a series of bones called 

 vertebrae, closelj- connected by means of fibrous and elastic structures, which 

 allow of a certain but limited amount of motion between them. In the \"oung 



