THE BODY SENSORY OR SOMESTHETIC AREA 



60 3 



It has already been shown that the motor fibers of the internal capsule of 

 one side cross over to the opposite side in the decussation of the pyramids in 

 the medulla. This decussation is not quite complete, as some fibers pass 

 down on the same side in the direct pyramidal tract. A small portion of 

 these direct fibers end around the motor neurones of the same side, but the 

 great majority cross to the opposite side in the anterior commissure at some 

 lower lever of the cord. It follows that the motor areas of the cortex on one 



FIG. 404. Diagram to Show the Relative Positions of the Several Motor Tracts in 

 Their Course from the Cortex to the Crus. The section through the convolution is vertical; 

 that through the internal capsule, 1C, horizontal; that through the crus again vertical. 

 CN, caudate nucleus; O TH, optic thalamus; Z,2 andZ-3, middle and outer part of lenticular 

 nucleus; f, a, I, face, arm, and leg fibers. The words in italics indicate corresponding 

 cortical centers. (Gowers.) 



side control the muscular movements of the opposite side of the body, but 

 also to a slight extent those of the same side. As a matter of fact, disease in 

 the region of the fissure of Rolando is usually accompanied by a disturbance 

 of the motor function on the opposite side of the body, although there is 

 some slight motor disturbance on the same side. 



LOCALIZATION OF SENSORY FUNCTION IN THE CEREBRAL 



CORTEX. 



There is evidence that fibers from the nerves of special sense are specially 

 connected with definite and distinct parts of the cerebral cortex. 



The fibers from the sensory nerves, we have found, are connected with 

 the cerebral cortex by chains of neurones. These sensory paths, although 

 complex, are definite and distinct. Their cortical connections have been 

 mapped out with considerable definiteness. 



The Body Sensory or Somesthetic Area. The motor function around 

 the pre-Rolandic region for a long time obscured the fact that this region, 



