THE NERVOUS SYSTEM 



179 



Again, it is quite possible that, after removing the receiving 

 mechanism in the cerebrum, external stimuli may lead to 

 the usual response by acting through lower reflex arcs 

 (Fig. 97). Thus, if we suppose the receiving part of 

 the cerebrum connected with the reception of tactile im- 



RECCIVING. 







D14CHAP.C.ING. 



FlG. 97. Diagram to show how through reflex action of the lower arcs the action 

 of the higher arcs may be stimulated. 



pressions entirely destroyed, scratching the sole of the foot 

 may still cause the leg to be drawn up, just as if a sensation 

 had been experienced. Here although the upper arc is out 

 of action the lower arc still acts. 



In the lower animals, stimulation of a part of the brain, 

 if it be connected with the reception of impressions, may 

 cause the series of movements which naturally follow such 

 an impression. But these movements may also be caused 



B 



Of CM, 



