1042 



CORTICAL MOTOR REGION. 



[BOOK in. 



referring to the nerves concerned in carrying out the several 

 movements, though in doing so we must remember that there is 

 not an exact correspondence between the relative position of a 

 muscle along the axis of the body or along the axis of a limb and 

 the relative position along the cerebrospinal axis of the nerve or 

 nerves governing the muscle. We may however, adopting this 

 method, note that the sacral and lumbar nerves are represented by 



FIG. 127. MESIAL ASPECT OF THE LEFT HALF OF THE BRAIN OF MACACOS, DISPLAYED 

 BY SECTION IN THE MEDIAN SAGITTAL PLANE AND REMOVAL OF THE CEREBELLUM. 

 Natural size. (Sherrington after Horsley and Beevor.) 



The hatched and stippled parts of the surface shew the regions of the cortex 

 connected with movements of the foot, knee, hip, tail, trunk, and neck 

 respectively. The several positions of the areas of cortex connected with 

 vision, and smell and with cutaneous sensation are indicated by the appropriate 

 words. 



The plane of section has passed through the corpus callosum, cc, cc, cc, and through 

 the anterior commissure, c, sparing the left pillar of the fornix, F ; behind it 

 has bisected the anterior part of the pons, laying open the aqueduct, Aq. (iter 

 a tertio ad quartum ventriculum). Pons, the left half of the pons in frontal 

 section. Op. the optic commissure cut across. 



III. the root of the third cranial nerve. 



FR. the frontal pole, 0(7. the occipital pole ; Cn. the cuiieus, Pen. the precuneus ; 

 G. fn. G. fn. G. fn. the gyrus fornicatus ; the unlettered fissure seen to form 

 the upper boundary of this gyrus in its supra-callosal part is the calloso- 

 marginal, Po.f. the parieto-occipital fissure. 



the most mesial portion of the whole motor area and by the hind 

 division of this mesial portion; that the lumbar and thoracic nerves 

 are represented by the front division of the same mesial portion ; 

 that the upper thoracic with the lower cervical nerves belong 

 to a region lying lateral to, and the upper cervical nerves to one 

 lying in front of the preceding area ; and lastly that the remaining 

 lateral and ventral portions of the whole motor region appertain to 

 the cranial nerves. But the topographical differentiation does 



