MUSCLES AND MOTION 85 



muscle? Is it elastic? Why should you expect this from its 

 use? 



Remove the skin from the sides of the body. How do 

 the underlying muscles differ from the leg muscles? Have 

 they tendinous ends? What two classes of muscles based 

 upon their form can you name from your study? Mention 

 some other parts of the body where these kinds of muscles 

 can be found. 



Preserve the rest of the rat's body for future use. 



LIV. GROSS STRUCTURE OF MUSCLE. 



Apparatus. A bellied muscle from the rat or frog (a piece of 

 fresh beef will serve), needles, compound microscope and slides, food- 

 testing materials. 



Directions. Boil the muscle in water for a few moments 

 and pick it to pieces with the needles. Note that it sepa- 

 rates easily into bundles. Why is cooked beef more easily 

 chewed than raw? Examine the perimysium covering the 

 bundles. What sort of tissue is it? Describe its appear- 

 ance. What purpose does it serve? Place one of these 

 bundles in a drop of water on a slide and with the needles 

 tear off the perimysium and tease the bundle into fibers. 

 Examine one of these fibers under the low power of the 

 microscope. Note its covering (sarcolemma) and its striated 

 appearance. All muscles under direct nerve control (vol- 

 untary muscles) show this striation. (For the minute 

 anatomy of this fiber see Ex. XXVII.) 



Apply the xanthoproteic and other food tests to pieces of 

 the muscle. From the strength of the various reactions, 

 what is the main constituent of muscle? Why does an 

 athlete require a diet rich in proteid ? 



