24 ANA7 OMY. 



some other motion, as for instance rotary or lateral movement. 

 We may find a type of this articulation between the temporal 

 and inferior maxillary bones, or between the femur and tibia. 

 Articulations of this kind are formed by oval heads fitting in oval 

 sockets. 



Gliding joints permit only simple gliding" movement between 

 the articular surfaces. The articular surfaces in joints of this 

 kind are more or less nearly flat. 



Immovable. — At immovable articulations the bones are firmly 

 united by cartilage and practically continuous with each other. 



Slightly movable. — At slightly movable articulations, bones 

 are united by a cartilage which is clastic enough to permit of slight 

 movement, e. g\, the common intervertebral articulations. 



At freely movable articulations the articulating bony surfaces 

 are each covered by a thin layer of smooth, glistening and elastic 

 articular cartilage. This cartilage gives a smooth gliding surface. 

 It also lessens jar by its elasticity and protects the bony surface 

 beneath. 



Structures at joints are bones, ligaments, tendons, muscles, 

 synovial membrane, and synovial fluid. 



Ligaments are either bands or sheets of white or yellow con- 

 nective tissue. The white ligaments are very strong and inelas- 

 tic. Their sole function is to hold bones together at articula- 

 tions. The yellow ligaments are composed of yellow elastic con- 

 nective tissue, and are especially useful as assistants to muscles, 

 particularly in supporting parts of the body, like the head of the 

 horse, which constantly tend to fall. 



Synovial membranes are sometimes called capsules. These are 

 serous membranes, quite thin, but composed of two layers, deep 

 and superficial. This membrane affords at each joint a closed 

 sack and is for the purpose of secreting synovia. Synovial mem- 

 branes do not cover the surface of the articular cartilage as is 

 frequently supposed, but usually enclose the articulations like 

 sacks, being attached at one side near the edge of the articular 

 surface of one bone, and at the other side near the articular edge 

 of the other bone. The membranes are usually also attached to 

 the inner surface of the capsular or other ligaments of the joint. 



Synovia is a viscid fluid, slightly yellow or nearly colorless. 

 It has an oily feeling, but is not an oil chemically. This fluid is 

 quite rich in albumen which gives it the viscid property, and 



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