EXERCISE 87 



In animals with a brain there is neither consciousness of any sensation or pain, nor control of 

 movements, except through the action of brain cells. Nevertheless, many stimuli produce responses, and 

 many connected movements can be performed, after the brain is removed or after its connection with 

 the other organs has been broken. This is illustrated by the chicken that runs around after the head is 

 cut off, or by the snake that moves about and withdraws from disturbing contacts after the head is removed. 



Problem. Can an animal make useful movements without the action of its brain ? 



What to use. A frog from which the brain has been cut away while under the influence of chloro- 

 form. Some dilute hydrochloric acid. 



What to do. Suspend the frog by the lower jaw from a suitable support. Touch the side of the 

 body lightly with a straw and note any reactions. Place a small piece of filter paper moistened with very 

 dilute acid on the side of the body, and note reactions. Place the frog on a table in a sitting posture and 

 tickle the sole of the foot ; note response. 



Record. Describe the reaction of the frog to the various stimuli applied, and show how any of them 

 might be considered of value to a frog under natural conditions. 



Questions. 1. Recall two changes in your own behavior which may be of use, but over which you 

 have no control. 



2. What reactions to stimuli do you know in your own body that are of no use to you ? 



[94] 



