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ELEMENTS OF PHYSIOLOGY 



dogs, and by studying cases of accidents to the skull in 

 human beings, this area has been subdivided. Stimulation 

 of the lowest part causes movements of the face ; of the 

 middle part, the arm ; and of the upper part, the leg, the 



FiG. 207. Diagram of the Motor Area and the Motor Tract in the Brain. 



Find centers for leg, arm, face. Notice that most of the motor fibers from one hemisphere 

 cross to the opposite side of the spinal cord; and if one half of the brain is injured the 

 opposite half of the body loses motion and sensation (paralysis). 



Trace nerve impulse from cell in cortex at i to muscle at 7. 



Trace reflex impulse from skin at to muscle at 7. 



movement always being on the side opposite to the stimu- 

 lation. When the lowest part of the area on the left side 



