TO f;0r; TO 



THE TISSUES 



35 



connective tissue, "blood vessels, lymphatics, and nerves, with 

 layer upon layer of bone concentrically arranged around it. 

 This constitutes an Haversian system. In this way the 

 characteristic appearance of the shaft of a long bone is 

 produced (fig. 14), with layers of calcified fibrous tissue, the 

 bone lamellae, arranged as Haversian, interstitial, peripheral, 

 and medullary lamellse. 



One important function performed by the cartilage is in 

 bringing about the increase in length of the bones. In 

 addition to the centre of ossification in the shaft, at each 



FIG. 14. Cross section through part of the shaft of an adult long bone to show 

 the arrangement in lamellse distributed as Haversian (1), interstitial 

 (2), peripheral (3), and medullary (4). 



end of the bone one or more similar centres of ossification 

 form. These are the epiphyses. Between these and the 

 central rod of bone the diaphysis a zone of cartilage 

 exists until adult life, when the bones stop growing. In 

 this zone, the cells arrange themselves in vertical rows, divide 

 at right angles to the long axis of the bone and form 

 cartilage. This cartilage as it is formed is attacked by the 

 bone-forming changes at the diaphysis and epiphyses, but 

 the amount of new cartilage formed is proportionate to this, 

 and thus a zone of growing cartilage continues to exist until 

 early adult life, when epiphyses and diaphysis join and 



