286 



THE GROWTH OF THE BRAIN. 



tions, but a vast number of irregularities, some of which 

 can be explained. 



For example, let the subject gradually fall asleep, the 

 knee-kicks become less and less extensive, as can be 

 seen by the accompanying graphic record ; then sud- 

 denly it becomes vigorous again. 1 



This revival may be caused by any sort of stimulus 

 the passing of a heavy cart, the dropping of a pencil, a 





FIG. 64. Record of the knee-kick of a demented patient. The 

 knee was tapped at regular intervals of five seconds. While 

 the patient was asleep and all about was quiet no response 

 was obtained. After such an irresponsive period the sound 

 of some one walking on the floor below caused at A a series 

 of kicks, which gradually diminished, the same at ./>'. At C, 

 two taps with a pencil and a distant locomotive whistle pro- 

 duced a longer series. The arrow indicates the direction in 

 which the record is to be read. (Noyes.) 



flash of light, or irritation of the skin. In each case the 

 result is an increase in the extent of the knee-kick, as 

 shown by the increased length of the verticals in the 

 graphic record 2 (Fig. 65). 



The feature in these results most important for us is 

 this the nerve cells controlling the knee-kick are located 



1 Noyes, Am. Journ. of Psychology, 1892. 



2 Lombard, Am. Journ. of Psychology, 1887. 



