166 ADVANCED LESSONS IN PKACTICAL PHYSIOLOGY 



3. Reaction to Sound. Arrange in series 2 or 3 dry cells, a simple 

 key, a signal, a hammer, and a metal plate. Arrange to record the 

 movements of the signal and of a tuning-fork. Let the subject hold 

 the key closed. Let the observer spin the drum and sharply tap with 

 the hammer upon the plate, thereby making the circuit. Let the sub- 

 ject open the simple key as soon as he hears the sound. Determine 

 the average reaction time of several tests of this kind. 



4. Reaction Time with Choice. Arrange the electric apparatus for 

 stimulation with single induction shocks and insert a signal and two 

 simple keys in the primary circuit. Connect the secondary coil with 

 a rocking bridge or mercury pole changer, and, in turn, each pair of 

 connectors with electrodes. Let the subject hold the electrodes to his 

 tongue, one on each side of it, and instruct him to open his key only 

 when the right side of his tongue has been stimulated. Shield the 

 apparatus by a large cardboard. Set the rocking key for stimulation 

 of either side of the tongue. Spin the drum and close your key. Re- 

 peat several times, changing the point of stimulation, so that the sub- 

 ject is forced to judge which side has been stimulated. Does choice 

 prolong the reaction time? 



5. Patellar Reflex Time. Let the subject be seated and cross his 

 legs. Adjust to the thigh of the crossed leg a rubber cuff, and connect 

 the latter by means of rubber tubing with a recording tambour. Ad- 

 just a tuning-fork upon a separate stand and arrange it to register its 

 vibrations from left to right, i. e., against the direction of rotation of the 

 drum of the kymograph. Spin the drum and tap the patellar ligament 

 of the subject, while he endeavors to reinforce the patellar reflex by 

 simultaneous efforts. The record of the tambour will show two 

 oscillations, namely, a wave due to the blow upon the ligament and 

 one caused by the contraction of the muscles of the thigh. Draw an 

 ordinate at the beginning of each wave, and determine the time which 

 has elapsed between the moment of stimulation and the reaction. 



6. Reflex Winking Time. Connect the upper eyelid of the subject 

 by means of a fine thread and soft wax with a recording lever. Insert 

 a signal in the primary circuit of an induction apparatus, and place the 

 writing point of the signal vertically below that of the recording lever. 

 Allow a tuning-fork to record below the signal. Place upon the lower 

 eyelid a pair of stimulating electrodes. While the drum is revolving 

 at a rapid rate stimulate with a single make or break shock of suitable 

 strength. Draw ordinates and measure the interval between the mo- 

 ment of stimulation and the moment when the upper eyelid began to 

 react. 



