GENERAL PHYSIOLOGY OF THE CEREBRUM. 187 



bility, but especially the former. It was suggested, therefore, 

 at one time that one and the same spot in the cortex might 

 serve as the origin of the motor impulses to a given muscle and 

 as the cortical termination of the sensory impulses coming from 

 the same muscle, the reaction in consciousness, the muscular sensa- 

 tions, being mediated perhaps through cells other than those 

 giving rise to the pyramidal fibers. Recent physiological and clin- 

 ical work has, however, not tended to support this view. The 

 motor areas appear to be confined to the region in front of the fis- 

 sure of Rolando, while the cortical area w r hich gives rise to that 

 kind of consciousness that we designate in general as body sensi- 

 bility extends back of the Rolandic fissure in the posterior central 

 gyrus. Whether, on the other hand, the sense areas for the body 

 (cutaneous and muscular) extend forward into the cortex of 

 the frontal lobe is not clearly shown by experimental or clinical 

 evidence. Flechsig, from his studies upon the time of myelini- 

 zation of the afferent fibers in the embryo brain, concludes that 

 this is the case, and that therefore the motor and sensory areas 

 overlap for a part at least of their extent (see p. 210 and Fig. 93). 

 In the motor area there are numerous connections by afferent 

 fibers, association tracts, with other parts of the brain. By 

 this means the motor area, without doubt, is brought into rela- 

 tion with many other parts of the cortex, and the sensations or 

 perceptions aroused elsewhere may react upon the motor paths. 

 A voluntary movement, however simple it may be, is a psychological 

 act of some complexity. The mental processes that lead to and 

 originate the motor discharge cannot be located in the cortex, but 

 the immediate origin of the motor impulse lies most probably, in 

 the areas along the anterior margin of the fissure of Rolando. 



