THE BODY-SENSE AREA 215 



affected. These muscles are bilaterally represented in the brain, 

 so that they remain under voluntary control when the motor 

 area of one side is destroyed. Mellus has shown that destruc- 

 tion of the centre of the great toe in monkeys is followed by a 

 degeneration down both crossed pyramidal tracts. Whether 

 the motor areas are only motor in function or include mechan- 

 isms serving sensation is difficult of determination. In two cases 

 recently reported, where the anterior central convolution was 

 stimulated in conscious patients, there was no sensation other 

 than that arising from the change in position of the muscles 

 thrown into contraction. 



The Body-sense Area. Lying posterior to the fissure of Rolando 

 lies an area which is concerned with cutaneous and muscular 

 sensations. There are cases on record in which lesions involving 

 the anterior central convolutions were accompanied by par- 

 alysis on the other side without any detectable disturbance of 

 sensibility, and, on the other hand, lesions of the posterior 

 central and neighboring parietal convolutions have been de- 

 scribed in which there was hemianesthesia without any par- 

 alysis . Lesion of the postcentral convolution, the supramarginal, 

 the superior and possibly inferior parietal convolutions seem to 

 involve chiefly muscular sense, pressure and temperature 

 sense, and the judgments and perceptions based on these sen- 

 sations, while the sense of pain is affected but little. Clinically 

 the most positive and invariable symptom of lesions in this 

 region is astereognosis, i. e., a loss of the power to judge the 

 form and consistency of external objects when handled. The 

 area of the cortex concerned with the sense of pain has not been 

 determined. 



The paths followed by various cutaneous impulses as well 

 as by those arising from muscles, tendons, etc., have already 

 been traced in the cord. Some of these were found to lead to 

 the nucleus gracilis, and to the nucleus cuneatus of the medulla. 

 At this point a second set of sensory neurons arises, which 

 for the most part runs ventrally as internal arcuate fibers, 

 crosses the midline just in front of the pyramidal decussation, 

 forming the sensory decussation. The path is then continued 

 forward in the median fillet or lemniscus, and thus reaches the 

 superior colliculus of the corpora quadrigemina and the thala- 

 mus. The important termination being in the ventral or lateral 



