642 



THE NERVOUS SYSTEM 



The relative position of the centers is probably much the same as in the 

 monkey's brain, those for the leg above, those of the arm, face, lips, and 

 tongue from above downward. Destruction of these parts causes paralysis, 

 corresponding to the district affected, and irritation causes contractions of 

 the muscles of the same part. Again, a number of cases are on record in 

 which aphasia, or the loss of power of expressing ideas in words, has been 

 associated with disease of the posterior part of the lower or third frontal con- 



CAUOSUM 



COftP;GEN:iNT. 

 SUP QUADV BODY 



PHALON 



TEMPORO-PONTINE 

 TRACT 



LOBE. 



FIG. 403. Diagram of Certain Connections of the Frontal, Temporal, and Occipital 

 Lobes. Founded on the observations of Flechsig, Ferrier, and Turner. (Cunningham.) 



volution on the left side. This condition is usually associated with motor 

 paralysis on the right side of the body, right hemiplegia. 



This district of the brain, particularly the convolutions bounding the 

 fissure of Rolando anteriorly, is now generally known as the motor area. 

 There is now no doubt whatever that this area gives origin to the nerve fibers 

 which proceed to the spinal cord, and are there represented as the pyramidal 

 tracts. 



This is the reason that movements are produced on stimulation of the 



