MUSCLES AND MOTION 



LIII. DISSECTION OF THE MUSCLES. 



Apparatus. The body of the rat used in Ex. XXXIII (any 

 other animal will serve the purpose and if a demonstration is desired 

 for the study of the leg muscles the leg of a sheep may be substi- 

 tuted), scalpel. 



Directions. Carefully cut off the hind leg of the rat, 

 close to the hip joint, and remove the skin. Note the 

 muscles covering the bones arid the glistening white muscle 

 sheath (perimysium) covering each muscle. At the ends 

 of the muscles note the white tendons. Are the muscles 

 attached directly to the bones? The end of the muscle that 

 moves most in contraction is called its insertion; the one 

 that moves least, its origin. Where are the tendons most 

 numerous? How does this arrangement avoid clumsiness 

 in the foot? Compare with the arrangement in your own 

 hand and foot. Is it the same? 



Separate the tendons and muscles without cutting them, 

 and pull on each to determine what part of the leg it con- 

 trols. Muscles that extend a joint are called extensors, 

 those that bend it are called flexors. Note that all these 

 muscles have a thick center, or belly, and tapering ends with 

 tendons attached at the ends. Those muscles with two ten- 

 dons at the origin are called biceps; those with three, triceps. 

 Examine one of these tendons. How is it different from a 



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