THE PHYSIOLOGY OF THE MUSCULAR SYSTEM 225 



contraction of which a muscle fibre is capable is approximately 47 

 per cent, of its resting length. Both Weber and Strasser looked upon 

 this as the factor which determines the length of the muscles, and the 

 location of their points of origin and insertion. In all of the skeletal 

 muscles the tension of the contracting muscle is greater than the 

 weight lifted. The farther the insertion of a muscle from a joint 

 (fulcrum), the less the tension upon the muscle and the greater the 

 amount of contraction or shortening necessary; but the inherent 

 structure of striated muscle tissue seems to set 47 per cent, as the 

 limit of the extent of its contraction. The fact that all skeletal 

 muscles actually do contract that much (varying, however, in special 

 instances from 44 per cent, to 62 per cent.) indicates that the position 

 of the origin and insertion or the length of muscle tissue (excluding 

 tendon) between the origin and insertion; or, more likely, that both 

 of these structural features have been determined by the laws of selection 

 and now represent in all highly organized animals the most perfect 

 mechanical adjustment consistent with the inherent properties of 

 muscle tissue. 



(1) Make a gastrocnemius preparation; measure the length of its 

 contractile tissue; mount it in the myograph; load it moderately; 

 stimulate it with optimum strength of stimulus, and determine from 

 the height of the myogram the actual shortening of the muscle. 

 What relation does this shortening sustain to the total length of the 

 contractile tissue? 



(2) Determine approximately the ratio of shortening to length of 

 contractile tissue in the human biceps. 



c. Problems in Human Locomotion. (1) The Muscles Used in. 

 Locomotion. Let a person stand erect with heels together; let him 

 take several steps forward and stop in a position similar to the one 

 which he had at the beginning. What is the mechanism of starting? 

 What muscles are involved in starting? What is the mechanism of 

 locomotion? W r hat muscles are involved in locomotion? What is 

 the mechanism of equilibration while walking? W T hat muscles are 

 involved in maintaining the equilibrium while walking? What is 

 the mechanism of stopping? What muscles are involved in stopping? 

 How is the equilibrium maintained during the process of stopping? 

 What muscles are involved in the maintenance of equilibrium while 

 standing ? How does running differ from walking in respect to the 

 starting, the locomotion, the equilibration, and the stopping? 



(2) The Energy Involved in Locomotion. How far is the body lifted 

 at each step when one walks over a level surface? When one walks 

 up an incline of 30 degrees? When one walks down an incline of 

 30 degrees? Does one do work while walking down hill? If so, 

 how may it be computed? If not, why does one become fatigued in 

 descending an incline ? How much energy will a 70-kilo man expend 

 in walking 1 kilo on a level road? (Suppose the man to be 172 cm. 



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