XXXVII.] 



PENDULUM-MYOGRAPH. 



207 



nerve over the electrodes in a moist chamber or use a crank-myo- 

 graph. Load tlie lever with 20 grams, and direct its point to the 

 side to wliich the pendulum swings. Yix the pendulum with the 

 detent, and adjust the writing-style of the lever on the smoked 

 surface. Connect the electrodes (or wires) from muscle or nerve to 

 the short circuiting key 

 in the secondary circuit 

 (omitted in fig. 125). 



After opening the 

 secondary circuit, with the 

 hand break the primary 

 circnit to make certain 

 that the muscle responds 

 at break. 



(d.) Close the trigger- 

 key (K') in the primary 

 circuit, and open the key 

 in the secondary circuit. 

 Allow the pendulum to 

 swing ; as it does so, it 

 knocks over the key in 

 the primary circuit and 

 breaks the current, thus 

 inducing a shock in the 

 secondary circuit, whereby 

 the muscle isstimulated and 

 caused to record its con- 

 traction or muscle-curve 

 on the smoked surface. 



(e.) Abscissa, i.e., the base line, 

 the muscle to remove the writing 

 recordinej surface. 



FlO. 125.— Scheme of the Arrangement of the Pen- 

 dulum. B. Battery ; /. Primary, //. Secondary 

 spiral of the induction raacliine ; S. T<ioth ; A''. 

 Key ; C, C. Catches ; K' in the corner, Scheme of 

 K' ; K. Key in primary circuit. It is well to have 

 a short-circuiting key in the secondary circuit. 



Rotate the stand supporting 

 point of the lever from the 

 Bring th(7 pendulum back to the detent, adjust 

 the writing-style, close the trigger-key, and keep the secondary cir- 

 cuit short-circuited. Allow the pendulum to swing. This records 

 the base line. 



(/) Latent period. — Bring the pendulum to the detent, short- 

 circuit the secondary circuit, and withdraw the writing-style as in 

 (e.). Close the trigger-key, with a finger of the left hand keep it 

 closed, allow the lever to touch the glass plate in its original posi- 

 tion, and with the right hand bring the knife-edge of the pendulum 

 in contact with the trigger-key, so as just to open it. A curved 

 line is inscribed on the stationary plate, which indicates the moment 

 of stimulation. 



{g.) Time-Curve. — Remove the muscle-lever, place the pendulum 

 in the detent, close the trigger-key, take a tuning-fork, vibrating. 



