ON VOLUNTAKY MOVEMENTS. 



667 



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 cerebro-spinal 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 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 



FIG. 149. 



Left Hemisphere of the Cerebrum of Monkey (Macacus), Viewed from its Left Side and from 

 Above. (Sherrington, after Horsley and Beevor.) Natural size. The figure shows the positions 

 of the portions of the cortex concerned with movement of various parts, and with the senses of 

 sight, smell, and hearing, The cortical area connected with the movements of the leg is shaded 

 vertically across, that with the movements of the arm horizontally, and that with the movements 

 of the trunk in a slanting direction ; the area connected with the movements of the head (neck), 

 face, and eyes is dotted. The course of the chief fissures is indicated by single lines. 



the front division of the same mesial portion ; that the upper thoracic with 

 the lower cervical nerves belong to a region lying lateral to, mid 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 

 not come out so clearly by this method as by that of taking for our guide 

 distinctive movements of the several parts of the body. 



It will be observed that all these areas taken together, represented by 



