LABORATORY MANUAL OF PHYSIOLOGY. 



cent solution of chloral hydrate. Test the reflexes as before and 

 compare with the normal taken as a standard. How does the effect 

 of the chloral compare with that of the strychnine? Repeat the 

 injection of the chloral until a lethal effect is produced. Note all 

 accompanying phenomena. 



II. REACTION TIME. 



1. For Sound. A tuning fork vibrating one hundred times per 

 second is placed in circuit with a time-marker. Two short-cir- 

 cuiting keys are placed in circuit with the time-marker, so that, by 

 closing either one, the time-marker may be cut out of the circuit. 

 The student experimented upon holds the handle of one key. An- 

 other student holds the handle of the other key. The first key is 

 held open, the second key being closed. Let the subject of the ex- 

 periment close his eyes. He should close his key as soon as he 

 hears the opening click of the other key. 



Theopening of the one key sets the time-marker to recording. 

 The closure of the other key stops the time record. This should 

 be taken upon a rapidly revolving drum. The interval between 

 the opening of the circuit and its closure is marked in hundredths 

 of a second and represents the time occupied for the passage of the 

 sound wave through the auditory apparatus, the auditory nerve to 

 the auditory centres of consciousness; its transfer to a motor 

 neuron; its passage to the muscles involved and the latent period 

 of these muscles. 



Repeat the experiment ten times for each individual and try 

 a number of different individuals. Estimate the average reaction 

 time for each individual. 



2. For Vision. For the first key to make the circuit, use a 

 mercury contact. Darken the room, so that the spark made when 

 the key is opened may be distinctly seen. Let the subject of the 

 experiment close his key as soon as he sees the spark made by the 

 opening of the other. The interval marked by the tuning fork 

 gives the reaction time for vision. This experiment should also 

 be repeated ten times and the average taken. 



