INTERNAL STRUCTURE OF THE BRAIN STEM 1015 



suniinatt'd hv the jjontilc- nuclei, sonu" conception ol tlieir significance may 

 be gained. Many of the jjallio-pontilc libers take origin in the parietal lobe, 

 from which region, in lact, they arise in greatest nuniber. This portion of 

 the neopallium is actixe in tlu' interc-st ol those e\tensi\e sensory syntheses 

 essential to gciu'ral body sensihilitx. In this broad area of tiie brain, all of 

 the myoarticular propriocepti\e organs haxe their cortical representation. 

 Here the impulses arising from such receptors become associated as kines- 

 thetic memories and guides lor directing all somatic motor acti\ities. 

 Impulses from other t\|)cs of receptors also find their ultimate area lor 

 elaboration m the parietal zone. .All \arietics of sensory stimuli arising 

 from the exteroceptors contribute to the upbuilding of discriminative 

 sensibilitx in the parietal lobe. The significance of the parieto-ponto-cerebellar 

 connection in tlu' interest of coordination therefore becomes ob\ious. 



In a similar manner, the large contribution of connecting fibers arising 

 m the temjjoroj^arietal region of the bram seems to have its explanation. 

 It is probable that in this territory the.' neopallium is acta e in the association 

 of those impulses \s hich arise in the xestilnilar projjrioccptors of the semi- 

 circular canals, utricle and saccule. Such impulses arc definitely connected 

 with the et]uilibratorv sense and, as such, play an important role in the 

 spatial orientation of the body, more jxirticularly of the head. The close 

 connection between the conscious fields of equilibratorv sense, of touch and 

 muscle-joint sense on the one hand, and the cerebellum on the other, serves 

 to perfect the coordinative control of muscular acti\ity. 



It has long been held that a Noluminous bundle of libers establishes 

 communication between the occipital lobe of the hemisphere and the lateral 

 lobe of tlu- cirebtllum. This fact has in recent times been called somewhat in 

 question and the large aggregation ol libers known as the occipito-ponto- 

 cercbellar fasciculus has been ascribed to origins intt'rmediate between the 

 parietal, temi^oral and occipital regions of the brain. \\ hether its origin is 



