112 NERVOUS SYSTEM. 



experiments for this reason, and it is probable that in them there 

 is a greater degree of this kind of response, though of the same 

 nature as in mammals. 



How are the reflex actions of the cord classified ? 

 Into cutaneous and muscular reflexes. 



What are cutaneous reflexes? 



Muscular actions which follow gentle stimuli applied to the skin. 

 The plantar reflex, or the motion of the toes and foot which occurs 

 on tickling the sole of the foot ; the cremaster reflex, or retraction 

 of the testicle by contraction of the cremaster when the inner side 

 of the thigh is stimulated ; and the pupillary reflexes, contraction 

 of the pupil to the stimulus of light, belong to this class of cuta- 

 neous reflexes. 



What are muscular reflexes? 



Muscular actions which follow a slight blow upon a muscle or 

 tendon when the muscle is in more or less tension. The patellar 

 reflex is a well-known example of this form of action : if the knee 

 be flexed to a right angle and the leg allowed to hang loosely, the 

 quadriceps femoris muscle is made moderately tense. . A gentle 

 tap upon the tendon of the muscle below the patella will cause the 

 muscle to contract and the leg to be more or less extended. These 

 reflexes are sometimes called tendon reflexes. 



What is inhibition of reflex action ? 



The ability to control or modify reflex action by an effort of the 

 will or by mental action which is not consciously voluntary. As 

 an example of this, if the palm of a sleeping child be touched by 

 the finger, the baby's hand will grasp the finger ; but if the child 

 is awake, no such reflex occurs, but is checked by mental action. 

 Again : one may avoid crying out when in pain by an effort of the 

 will, or may hold the feet still when the soles are tickled. 



Are reflex actions frequent in the ordinary acts of life ? 



They are. An ordinary act which has become habitual for 

 example, walking while at the first it is performed as a voluntary 

 muscular act, becomes reflex and is performed without conscious 

 control of the mind, and is more easily and more gracefully done 

 when no attempt is made to direct the actions of the muscles 

 involved. 



