26 VETERINARY STUDIES 



membrane are always serious, as for example, "open joint," and 

 this is true of all serous membranes in general. 



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 adapts it so well for lubricating articular surfaces. Muscles 

 and tendons are discussed in Lecture VII. 



Kinds of motion. — These are : flexion, or bending, in which the 

 two articulating bones are brought nearer each other ; extension, 

 the reverse of flexion, by which bones are straightened on each 

 other; adduction, bringing the lower extremity of the moving 

 bone toward the median line; abduction, in which the lower 

 end of the moving bone is carried from the median line ; circum- 

 duction, in which the articulation forms the apex of a cone cir- 

 cumscribed by the moving bone; rotation, in which one bone 

 rotates as a pivot on another. 



Joints are named according to the bones involved. In the 

 limbs the upper bone is named first. In the vertebrse, the an- 

 terior bone is named first. 



Describing Articulations, Examples ^ 



Scapulo-humeral articulation. — This is a ball-and-socket joint, 

 the rounded head of the humerus fitting the glenoid cavity of 

 tlie scapula. 



Ligaments at this joint are: (a) glenoid, a cartilaginous rim 

 around the cavity which deepens the cavity; (&) capsular, a 

 sort of capsule fitting around the joint like a bag; (c) two 

 bundles of ligament fibers in front of the joint connecting the 

 extremities of the scapula and humerus. 



Movements. — All the motions, except true gliding, are pos- 

 sible at this articulation. The synovial membrane is quite loose 

 and affords a lining for the capsular ligament. 



First interphalangeal articulation. — This is an imperfect 

 hinge joint. The articular surface of the inferior extremity of 

 the first phalanx is characterized by two condyles and a median 

 groove which fit with two shallow cavities and a median ridge 

 on the superior extremity of the second phalanx. 



Ligaments. — The articular extremities which make up this 



articulation are supported by the following ligaments and ten- 



^ All freely movable articulations are described in this general way 

 in anatomy. 



