380 APPLIED PHYSIOLOGY 



11. By exercise of the muscles, the nutrition of the whole 



body is improved. 



12. Too much exercise uses the power which should go 



to the brain and other organs and so harms the 

 body. 



13. That form of exercise is usually best which most 



interests a person. 



DEMONSTRATIONS 



165. Skin a chicken's leg and separate each muscle. Show their 

 broad upper attachments and the small tendons into which the lower 

 ends taper. Cut off the skin from the lower parts of the legs and toes 

 and show how the tendons are attached to the toes. Notice that bend- 

 ing the leg tightens the tendons and flexes the toes. Explain how this 

 compels the toes to grasp the perch while the fowl is roosting. Pick a 

 muscle apart to show the separate fibers. Sketch a muscle. 



1 66. Point out the main groups of muscles upon a boy. Have him 

 perform such motions as raising his arm and clenching his fist, and feel 

 what muscles are in action. Notice that when one set of muscles is in 

 action the opposing set also acts so as to steady the limb. Point out 

 the tendons, especially in the wrist and knee. 



167. With two needles tear apart a small shred of muscle from a 

 piece of cooked meat and examine it under the microscope with a power 

 of at least 200 diameters. Sketch the ribbonlike muscle cells and their 

 fine cross markings. Notice the small amount of wavy connective 

 tissue between the cells. Examine a prepared specimen to show the 

 cells cut across and the capillaries surrounding the cells. 



168. Show involuntary 'muscle cells by preparing a shred from a 

 fowl's gizzard, as in demonstration 167. Sketch the specimen. 



169. Hold a pencil firmly with the elbow flexed. Contract all the 

 muscles of the arm strongly. Notice that the whole arm trembles. 

 Now let the pencil tap the table by means of this trembling motion, and 

 notice that the taps are about ten a second. Explain that the taps are 

 due to successive motor impulses from the brain. Now tap the table 

 rapidly with the ordinary motion of the hand. Notice that it can be 

 done only about five or six times a second. Explain that in this case the 

 mind must cause two separate sets of muscles to contract alternately. 



