114 EXERCISE XVIII 



the stop. Lift the recording-lever by placing a finger under its distal end, 

 and raise the lever till the point of it is near the level of the top of the 

 drum. Withdraw the finger briskly so as to let the lever fall freely. Note 

 that after its fall the lever reascends and then drops again. This reascent is 

 partly due to mechanical vibration, but mainly due to a contraction of the 

 muscle in response to the sudden pull on the muscle produced by the fall of 

 the lever. 



Text-fig. 39. Proprioceptive reflex of tibialis anticus evoked by sudden slight 

 stretch, e. g. fall of lever (K. A. J. Mackenzie and N. L. Watt). The resulting 

 reflex is in this instance clonic, i. e. double (Asayama). t, time marked in -03". 



[Adjust drum-pulley so as to run as slowly as can conveniently be 

 managed. Rotate the standard carrying the myograph-lever up to the check- 

 stop at its base, so that its point touches the recording-surface. Lift the lever 

 with the finger as before. Let the drum run, and whilst it is running let the 

 lever fall as before. The reflex twitch produced by the fall is recorded (text- 

 fig. 39). Rotate the lever-standard to withdraw the writing-point from the 

 drum. Stop the drum. Screw up the after-load stop of myograph so as to 

 just support the lever when the muscle is quiescent.] 



^ r^ VII. A. Place the secondary coil at 25 cm. on the inductorium scale. 



Reflex of tibialis With the myograph-lever not touching the recording-drum, and, with the 



anticus to single bridge-key in secondary circuit closed, close the key in the primary circuit. 



rea -s oc . g^^ ^^^ drum revolving. Open the short-circuit key. Lightly strike open 



with the finger the key in the primary circuit. Note whether a contraction 



results. Repeat the manoeuvre, short-circuiting the make-shock each time, and 



