NERVOUS SYSTEM. 



3. For Tactile Sensation. The circuit-opening key may be 

 so arranged that, upon opening, it will come into sharp contact 

 with the finger of the subject who is to close his key as soon as he 

 feels this contact. This will give the reaction time for tactile 

 sensation. 



4. Influence of Drugs on the Reaction Time. Repeat 

 experiments i to 3 on one of the subjects whose normal reaction 

 time has already been determined, after drinking 30 c.c. of 

 whiskey diluted with equal parts of water. 



III. REMOVAL OF CEREBRUM IN THE FROG. 



Remove the cerebral hemispheres in a frog by making a cut 

 through the skull in front of the tympanic membranes. Compare 



t 2 



FIG. 19. Pigeon's Brain, i, Skull which has been removed in part to show relations 

 of cerebrum 1^2), cerebellum (3), and medulla (4). 



the frog so treated with a normal frog. Place both the normal and 

 the decerebrized frogs on their backs. How do they react ? Stim- 

 ulate the decerebrized frog. Is there any change in the co-ordina- 

 tion of movements? Place both frogs in water. Can the decere- 

 brized frog swim in a normal manner? 



Make cut behind the tympanic ' membranes. Compare this 

 condition with the preceding and with the normal. 



[51] 



