THE CENTRAL NERVOUS SYSTEM 375 



The eye will be closed involuntarily. 



3. Throat Reflex. Touch the posterior wall 

 of the throat. 



The movements of swallowing will 'usually 

 follow. 



4. Pupil Reflexes ; Light Reflex. Close one 

 eye for several seconds, then open it quickly. 



Note the contraction of the pupil. 



5. Consensual Reflex. Close one eye as before, 

 but watch the pupil of the other eye when the 

 first is opened again. 



The pupil will contract. 



6. Accommodation Reflexes. Look alternately 

 at a near and a far object. The pupil will con- 

 tract when the eye adjusts itself to see the near 

 object. 



TENDON EEFLEXES 



Knee Jerk. Sit in such a position that the 

 knee is bent at a right angle, and the foot hangs 

 free. Let an assistant strike the patellar liga- 

 ment with the side of the hand. 



Note the sudden contraction of the extensors 

 of the thigh, the so-called knee jerk. 



Flex the knee at different angles and deter- 

 mine in which position the resulting contraction 

 is greatest. 



Knee jerk can be obtained only within certain 

 limits of extension. 



