Conditional Reflexes 175 



is being fed and his salivary glands thus stimu- 

 lated, we prick or otherwise painfully stimulate 

 the animal's skin, he naturally shrinks from 

 our treatment; after a time, when the dog has 

 ceased eating, if we again apply a painful 

 stimulus to his skin he no longer shrinks from 

 it, but there is a marked increase in the 

 secretion poured out from his salivary 

 glands. 



From these and many other like experiments 

 it seems clear, that a nervous impulse resulting 

 from a stimulus which naturally passes to cor- 

 responding central nerve cells may, under new 

 conditions, be diverted to another centre that 

 is, it is easy by changing the conditions to 

 divert an impulse from one to another path. 

 It can be shown that processes of this kind 

 depend on the action of the living substance of 

 certain areas of the neopallium ; for if these 

 parts of the brain are removed during life, no 

 new or conditional reflexes can be established, 

 but if at the same time the basal and spinal 

 systems have been preserved, the animal 

 responds to stimuli by simple, or it may be 

 automatic, reflexes. 



