PEOPERTIES OF THE BONES. 



347 



first two cases also, there is frequently a cavity in the interior of 

 the connecting substance; so that the sacro-iliac symphysis in par- 

 Fig. 224. 



Insertion of the tendo-Achillis into the calcaneum of a man sixty years old. A. Bone with lacunae, 

 a ; cancelli and fat-cells, 6. B. Tendon ; with tendinous fibres and cartilage-cells, c. Magnified 300 

 diameters. (Kolliker.) 



ticular may be regarded as a sort of movable articulation. (Zaglas.) 

 Some of the articulations of this class are also surrounded by liga- 

 ments, described in all anatomical works. 



In the synarthroses, the bones are united merely by an extremely 

 thin membranous whitish streak, incorrectly termed the sutural 

 cartilage. It is really white fibrous tissue, and it gradually disap- 

 pears in old age, and is at last in many parts entirely removed, 

 especially on the inner part of the sutures ; and even before the 

 complete obliteration of the latter. It is properly termed the sutural 

 ligament, therefore. 



Properties of the Bones. 



The properties of the bones are those of the osseous tissue, 

 already specified (p. 335), the most important being their rigidity 



