LESSON VI 

 MUSCLE AND NERVE (Continued) 



CONTRACTION OF HUMAN MUSCLE. INFLUENCE OF BLOOD-SUPPLY. 



SMOOTH MUSCLE 



1. Contraction of Human Muscle. Adjust your right forearm in 

 the holder of the ergograph and place the middle finger in the sling 

 supporting a weight of 2 to 3 kilos. Attach a pointer to the latter, 

 permitting it to rest against the paper of a kymograph. Make several 

 voluntary contractions upon a rapidly revolving drum and above the 

 record of a tuning-fork. Estimate the amount of work accomplished 

 each time. 



FIG. 30. Mosso's ERGOGRAPH. 



C is the carriage moving to and fro on runners by means of the cord d, which passes 

 from the carriage to a holder attached to the last two phalanges of the middle finger 

 (the adjoining fingers are held in place by clamps); p, the writing point of the carriage, 

 c, which makes the record of its movements on the kymographion ; w, the weight to be 

 lifted. (HoweU.) 



Use a very slow drum. Flex the middle finger and retain it in this 

 position until the end of the paper has been reached (tetanic contrac- 

 tion). Note the oscillations and resulting fatigue. 



Use a very slow drum. Flex the middle finger at a definite rate, 

 say, once in every second, until fatigue has resulted. Allow the speed 

 of rotation to be indicated by a chronograph beating at intervals of two 

 seconds. 



Annotation. If Mosso's ergograph is not available, use a spring ergograph which 

 consists of a horizontal lever attached to a metal upright. The fingers of the right 

 hand are securely fastened in a holder, while the index-finger of the same hand is 

 abducted against the lever. Isotonic contractions are obtained if the rod resting 



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