REFLEXES 



95 



The beginner naturally thinks of the sense-organs as 

 existing for the acquisition of knowledge. This is 

 certainly an important aspect of their employment and 

 one which we cannot afford to slight in our later treat- 

 ment of the subject, but we must recognize first a lowlier 

 type of action. This is the reflex. We must take 

 great pains to define and illustrate what is meant. 



FIG. 24. The principle of reflex action. The subject touches a hot 

 object (#) Afferent nerve-impulses travel the route marked by dots 

 and dashes to the spinal cord OS). Efferent impulses return promptly 

 along the route marked by little crosses to the muscle (M), which 

 cooperates with others not shown to withdraw the finger from the 

 stimulating surface. The situation of the coordinating center is left 

 undetermined, as far as this diagram is concerned, whether in the brain 

 or the cord. 



Examples are numerous enough but they are apt to 

 admit of misconceptions. 



A reflex act is one which is executed in response to an 

 external stimulus. It is desirable to add that it is an 

 act not requiring attention. Take for instance the case 

 most often cited, that of the quick withdrawing of the 

 finger from a hot object. A child who made the trial 

 would probably say that he felt pain and took his finger 



