THE NERVOUS SYSTEM 273 



turn the block the frog can be made to creep around it 

 almost indefinitely. Thus it not only maintains the erect 

 position but also corrects loss of equilibrium by appropriate 

 balancing movements. 



(3) If the frog be stroked upon its belly, it will croak; 

 if its lips be touched with a blunt pin, it will brush the pin 

 away with its forefoot. Most important of all, if it be thrown 

 into the water, it will swim; and when it reaches a solid 

 object it will crawl out upon it and come to rest. In short, 

 the animal will carry out almost any movement of which a 

 normal frog is capable, provided the proper stimulus is applied ; 

 but without this it will do nothing, though capable of doing 

 so much. 



The facts thus far brought forward show that the neurones 

 of the 'tween, mid, and hind brains and of the spinal cord 

 constitute nervous mechanisms which can maintain the nor- 

 mal posture, correct loss of balance, and even carry out the 

 usual acts of locomotion. The more of the nervous system 

 which the animal retains, the more complicated are the move- 

 ments, as we should expect when we remember the increase 

 in the number of neurones and the greater complexity of 

 coordination thereby rendered possible. 



8. Comparison with the normal frog. The behavior of a 

 frog lacking only the forebrain, or cerebrum, differs from 

 that of a normal frog in two most significant respects. In 

 the first place, the animal rarely makes any movement with- 

 out obvious external stimulation ; if protected from drying, 

 it will often sit motionless for days, or even weeks. Such is 

 not the conduct of an animal which is aware of what is going 

 on around it or of its own sensations or feelings, that is, of 

 a conscious animal. In the second place, the frog shows the 

 most remarkable regularity and persistency in making re- 

 peatedly the same response to the same stimulus ; if its lips 

 be touched thirty times with a blunt needle, it will brush 

 at the offending object every time in the same way with the 



