270 PHYSIOLOGY. 



eral anesthesia. Whenever the sound eye was closed he 

 went to sleep." -FOSTER. 



Let us turn from the consideration of outgoing, or 

 efferent, nerve impulses and their resulting action to the 

 incoming, or afferent, nerve impulses and the activity 

 which they rouse in the gray matter of the cerebrum 

 sensation. 



READING. Wear and Tear, Mitchell ; Power through 

 Repose, Call ; Technique of Rest, Brackett. 



Summary. i. Nerves may be stimulated by mechanical force, 

 chemical action, heat, and electricity. 



2. Electricity is the most convenient nerve stimulus for physiological 

 experiment. The induction current is usually employed. 



3. To increase sensations arithmetically stimuli must increase geo- 

 metrically. 



4. Reaction time is the interval between the application of a stimu- 

 lus and the response. 



5. Sensations are relative. 



6. Habits are acquired reflex actions. 



7. The nervous system is unlike the telegraph system in using one 

 set of fibers for receiving and another for sending messages. 



Questions. i. Is the difference in "reaction time 11 in individuals 

 of any significance ? 



2. Why are slight wounds in a battle often unperceived ? 



