MUSCLE-NERVE. 



and adjust the writing point against the smoked paper of a drum. 

 The lever should be nearly tangent to the surface of the drum and 

 the drum should revolve away from the point of the lever. Ar- 

 range the drum so that it may be revolved by hand. 



1. To Show the Elasticity of a Rubber Band. Attach a rub- 

 ber band to the femur clamp and myograph lever and adjust for 

 writing on the smoked drum. Carefully place a lo-gram weight in 

 the pan attached to the lever. Move the drum slightly to record 

 the amount of stretching. Remove the weight, allow the lever to 

 return through the elasticity of the band and revolve the drum 

 again slightly. Repeat this with 20 grams, with 30 grams, with 40 

 grams, with 50 grams. Does the lever return each time to its orig- 

 inal position ? 



2. To Show the Elasticity of Muscle. Repeat the above ex- 

 periment, using the muscle already prepared. How does the elas- 

 ticity of the muscle compare with that of the elastic band ? If the 

 elasticity is not perfect for the amount of stretching force em- 

 ployed, are there any factors of error in the apparatus and 

 method that may, in part at least, account for the results ob- 

 tained ? 



3. To Show the Tensile Strength of Muscle. With the same 

 preparation used in the previous experiment, carefully add weights 

 to the pan of the lever until something gives way. Which breaks 

 first, the muscle or the tendon ? Prepare a fresh muscle and re- 

 peat, inserting needle electrodes into the muscle and stimulating 

 with a tetanizing current from an inductorium for each addition 

 of weight. How much will the muscle lift ? 



4. Hooke's Law. This is embodied in the statement that the 

 power of any spring is in direct proportion to the tension under 

 which it is placed. Does the muscle in experiment (b) respond to 

 Hooke's law where small weights are used ? Recent experiments 

 by Professor Haycraft, with improved apparatus from which all 

 sources of error have been eliminated, show that, within physio- 

 logical limits, all the simple tissues of the body follow this law. 



[21] 



