PHYSIOLOGY OF THE NERVOUS SYSTEM 323 



inhibited (prevented) ? Repeat the experiment, effort being made to 

 prevent the movement, but not by contracting opposing muscles. 



Other reflex actions adapted to class study are those of the eyes, 

 such as the closing of the lids on moving objects near them and the 

 dilating of the pupils when the eyes are shaded. The involuntary 

 jerking of the head on bringing the prongs of a vibrating tuning fork in 

 contact with the end of the nose is also a reflex action which can be 

 studied to advantage. 



To determine the Reaction Time. Have several pupils join hands, 

 facing outwards, making a complete circle, excepting one gap. Give a 

 signal by touching the hand of one pupil at the end of the line. Let 

 this pupil communicate the signal, by pressure of the other hand, to the 

 next pupil and so on around, having the last pupil raise the free hand 

 at close of the experiment. Note carefully the time, preferably with a 

 stop watch, required to complete the experiment and divide this by the 

 number of pupils, to get the average reaction time. The experiment 

 may be repeated with boys only and then with girls, comparing their 

 average reaction time. 



Reflex Action of the Salivary Glands. Place a small pinch of salt 

 upon the tongue and note the flow of saliva into the mouth. Try other 

 substances, as starch, bits of wood, and sugar. What appears to be the 

 natural stimulus for these glands ? Compare with reflex actions of the 

 muscles. 



