6 LESSONS IN HORSE JUDGING. 



repeated, the parts would become heated by friction 

 were it not that this is provided against. Friction 

 is prevented by the tendon being surrounded by a 

 sheath, containing a lubricating material called 'joint 

 oil' or technically^ ' synovia.' This ' joint oil' or 

 ' synovia' is generated by a membrane lining the 

 * sheath,' and which gets the name of ' synovial 

 membrane,' because it produces the synovia. 



Some muscles do not terminate in rope-shaped 

 tendons which have to 'play' through lubricated 

 sheaths, but end in expanded sheet-like tendons 

 which need no lubricating material. We shall find 

 that the muscles of the face are of the latter 

 description, and have their sheet like tendons 

 closely connected to the skin over the lips. This is 

 well seen in ourselves in laughing. The bellies of 

 the muscles forming our cheeks contract and of 

 course swell out (Fig. 1. A)^ while their tendons 

 are attached closely to the skin of the lips, especially 

 the upper lip, so that in laughing the cheeks bulge 

 out and the lips tighten and drag backwards. 



9. — The contraction of a muscle is ver}^ limited, 

 so that the tendon moves a very little distance in 

 its sheath. 



So much for the active part of the lever, the 

 remaining parts are made up of passive agents in 

 the form of bones and joints. 



10. — Bones are of three varieties, named from 

 their shape ; long, flat, and irregular. 



The long bones are largely concerned in forming 



