494 



APPENDIX 



coil completely over the primary, open the short-circuiting key, and set 

 the vibrating armature in motion if not already vibrating. 



Connect one binding-post only of the secondary coil with the first of 

 the series of muscles. One after the others will contract stimulated by 

 the induced electricity "piled up" on the pole, for this electricity has 

 many of the characteristics of static electricity. 



(B) Remove three of the four muscles, and while the remaining one is 

 being stimulated as before, hold a moistened finger near the muscle. 

 The latter 'will contract, the stimulating tension being reduced suddenly 

 by withdrawal into the condensing human body. The practical moral 

 of this experiment is to always keep the short-circuiting key closed save 

 exactly when the induced electricity is being used, thus avoiding ex- 

 plosions of the sort demonstrated. 



FIG. 275 



FIG. 276 



Effect on the contraction of much increasing 

 the load. Each curve from left to right repre- 

 sents fifty grams more load beginning with the 

 lever's weight only. Frog's gastrocnemius. 

 Intervals of about forty-five seconds. 



Effect on the contraction of increasing 

 the load. Each curve from left to right rep- 

 resents ten grams more load beginning with 

 the lever's weight only. Frog's gastrocne- 

 mius. Intervals of about forty-five seconds. 



The theory of unipolar induction is practically given in the direc- 

 tions for the experiment; induced electricity when allowed to accumulate 

 on one secondary-coil pole has a high tension and the consequent 

 ability to jump through considerable spaces of non-conductors. In 

 practical neurology, for example, in testing muscles for reaction in cases 

 of disease, this principle is of great importance, and errors of diagnosis 

 may be easily made by disregarding it. 



Expt. 54. Influence of Load on Contraction. (Apparatus: Myo- 

 graph, inductorium, sartorius, various weights.) Set up the apparatus 

 for making myograms from the sartorius muscle, used in place of the 

 gastrocnemius. Use maximal break induction-shocks, cutting out 

 all the makes. With the drum stationary, record a contraction when 



