REFLEX ACTION. 



105 



time from a number of observations on the same subject. 



Each individual of the pair should serve as subject. 



There is no example of a postural reflex which can conveniently 

 be studied in the frog or man. (The extensor thrust and the mark- 

 time reflexes (see p. 240) of the spinal mammal will serve this 

 purpose) . 



The myotatic reflexes are best illustrated in the KXEE JERK. 



FIG. 31. Arrangement of apparatus for measurement of reaction time in man. 



Experiment 47. Let the subject sit in a comfortable position with 

 one leg crossed over the other so that the patellar ligament is 

 under an increased tension. The operator strikes the patellar 

 ligament a sharp blow with the edge of his hand or a book. 

 With a little practice it is easy to elicit a sudden contraction 

 of the quadriceps muscle giving a sudden extension of the leg. 



