THE CEREBRUM 



,ation are three tracts numbered by Flechsig i, 2 and 3,. which arise largely 

 torn the median nucleus of the thalamus and the medial lemniscus and pass 

 o the anterior and posterior convolutions, to the para-central lobule and 

 oot of the superior frontal convolution, and to the foot of the third frontal 

 Convolution respectively. It is these fibers which convey nerve impulses to 

 he cortex and furnish information regarding changes taking place in the 

 >ody itself and thus lead to the performance of muscle movements. This 

 ,rea is therefore primarily a sensor area, an area for body-feelings, cutaneous, 

 actile, muscle, and visceral, and secondarily a motor area. The afferent 

 ibers to this region become myelinated during the ninth month of intra- 

 iterine life, the efferent fibers from it become myelinated during the third 

 nonth of extra-uterine life. 



By the same method of reasoning the gustatory, olfactory, auditory, and 

 visual sense areas are to be regarded as sensori-motor in character, for embryo- 

 ogic investigations show that subsequently to the myelimzation of the 

 ifferent tracts connecting the sense-organs with the cortex, efferent nerve- 

 racts arise from or near to the same centers and undergo myelimzation. 

 )ther words, these areas are primarily sensor and secondarily motor, and 

 therefore should be termed sensori-motor. In Flechsig's own terminology 

 each corticopetal or afferent tract is accompanied by a corticofugal c 



^The view, viz. : the coincidence of sensor and motor areas has had general 

 acceptance for the reason that it seemed more in accordance with tl 

 than the earlier view. Nevertheless there were many facts both of a physio- 

 logic and pathologic character which were difficult to harmonize with it, am 

 in recent years the accumulation of facts and the weight **b" 

 toward the view that the areas are anatomically separate and 



the Chimpanzee Brain.-In a series of experi- 



ments mde by Sherrington and Grunbaum on the brain ^JgQ 

 it was discovered that the so-called motor area was not so widely distribu e 

 as in the monkeys generally, but was confined almost exclusively to the 

 KnWutLnuTt C front of the fissure of Rolando, as it was impossible to 

 oE any movement on direct stimulation of the convolution J 

 All points on the surface of the pre-central ^ ofeti ^S% 

 . formine- the wall of the Rolandic fissure itself, were found to be 

 ! Krfductive of movement when stimulated^ ^S^ 





areas 





