INDEPENDENT MUSCULAR EXCITABILITY. 157 



4. Rupturing Strain of Muscle and Tendon. 



(a.) Dissect out the femur and gastrocnemius with the 

 tendo achillis of a frog. Fix the femur in a strong clamp 

 on a stand, preferably one with a heavy base. To the tendo 

 achillis tie a stout thread, and hang a scale pan on to it. 



(6.) Into the scale pan place weights, and observe the 

 weight required to rupture the tendon or muscle. Usually 

 the muscle is broken first, and the weight added to the scale 

 will be a kilo, more or less, according to the size of the 



(c.) Compare the rupturing strain of a frog's gastrocnemius 

 which has been dead for twenty-four hours. A much less 

 weight is required. 



5. Muscle Sound. 



(a.) Insert the tips of the index fingers into the auditory 

 meatuses, forcibly contract the biceps muscles. A low 

 rumbling sound is heard. 



(6.) When all is still at night, firmly close the jaws, and 

 especially if the ears be stopped, the sound is heard. 



6, Dynamometers. 



(a.) Hand. Test the force exerted first by the right hand 

 and then by the left, by means of Salter's dynamometer. 



(b.) Arm. Using one of Salter's dynamometers, test the 

 strength of the arm when exerted in pulling, as an archer 

 does when drawing a bow. 



LESSON XXX. 



INDEPENDENT MUSCULAR EXCITABILITY 



ACTION OF CURARE ROSENTHAL'S 



MODIFICATION POHL'S 



COMMUTATOR. 



1. Independent Muscular Excitability and the Action of Curare. 

 Ourare paralyses the intra-muscular terminations of the motor 



