LABORATORY MANUAL OF PHYSIOLOGY. 



other muscles if the application of the stimulus is continued? 

 Explain. 



(b) Wash the foot thoroughly in plain tap water and dry with 

 filter paper. Repeat experiment (a), using a stronger solution of 

 the acid (i to 1000). Record reflex time as before. 



(c) Wash the feet again and dry with filter paper. Repeat ob- 

 servations, using a still stronger solution of acid (i to 500), and re- 

 cord results. What is the effect on reflex time of increasing the 

 strength of the stimulus ? 



(d) Instead of the acid, use medium make-and-break shocks 

 from an inductorium as the stimulating agent. Make and 

 break every three seconds for ten shocks. Is there any reflex 

 response ? 



(e) Increase the frequency of stimulation to one per second; to 

 two per second. Is there any reflex? If so, how many stimuli 

 must be applied to the skin before the reflex arc is completed? 



> Where are the main places of resistance in the reflex arc ? 

 i 2. Reflex Action with Optic Lobes also Removed. Using 

 the same frog as in the previous experiments, make an incision 

 through the skull and brain just behind the tympanic membrane. 

 Allow time for the nervous system to recover from the shock of the 

 operation before proceeding with the next series of observations. 



Repeat experiments (a) to (e) of series i. How does the reflex 

 time of this set of experiments compare with that of the previous 

 set? 



What is your conclusion concerning the influence of the optic 

 lobes, in the frog, on cord reflexes ? 



3. Reflex Action with Medulla Removed. Complete the 

 pithing of the frog and repeat the previous series of experiments. 

 Conclusions? 



J 4. Diffusion of Impulses within the Cord. Pith another 

 frog. Suspend as before. Apply a strong and continuous stimulus 

 to one foot. Note the successive groups of muscles that become 

 involved in the reflex reaction. Also note the time at which each 

 group becomes involved and the order of response. 



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