THE N1:R\ OUS SYSTEM 



539 



The pallium consists of an extensive external convoluted sheet 

 of gray matter {cortex pallii or cortex cerebri) and of white matter 

 underlying the gray. In the white matter may be (Hstinguished 

 the corona radiata comjioscd of the afferent and efferent i)a]Ual 

 fibres connecting the palhum with otlier parts of Ihf brain (projec- 

 tion fibres). The remaining iibres of the 

 white matter are association fibres of the 

 palUum and are either crossed or com- 

 missural, connecting the two hemispheres 

 {corpus callosum and fornix commissure), 

 or are uncrossed. The term association 

 fibres is often restricted to the uncrossed 

 fibres. 



The atlerent connections of the neopal- 

 hum (p. 529) and rhinopallium (p. 538) 

 have been summarized and also the efferent 

 connections of the rhinopallium (p. 538). 



The following are the principal descend- 

 ing or efferent connections of the neopallium : 

 (i) The pyramidal or pallio-spinal tract. 

 This is composed of the axones of the giant 

 cells (of Betz) of the arm, body, and legpre- 

 central motor areas. They descend in the 

 corona radiata, the posterior limb of the 

 internal capsule, middle part of the pes, 

 and thence through pons and medulla to 

 the cord. Their decussation and further 

 course has been described. (2) The de- 

 scending tracts to the motor nuclei of the 

 cranial nerves originate from precentral cells 

 of the various areas controlling the muscles 

 in question and pass down in the vicinity 

 of the genu of the internal capsule. Their 

 path is not so well known but they appar- 

 ently do not pass down in the pes through- 

 out their course (pp. 530, 527, etc.). (3) 

 The pallio-pontile system to the pons (continuation to opposite 

 cerebellar hemisphere). This originates in various parts of the 

 cortex. The fibres from the occipital (?) and temporal regions pass 

 down in the extreme posterior part of the internal capsule and lateral 



Fig. 360. — Scheme of 

 General Arrangement of 

 fibres in Internal Capsule, 

 (von Bechterew.) /, //, 

 ///, The three parts of the 

 lenticular nucleus; nc, nu- 

 cleus caudatus; F/;, thalamus; 

 gp, globus pallidus; pt, put- 

 amen; i, fibres of anterior 

 thalamic peduncle; 2, fibres 

 of medial (frontal) pons 

 system (frontal pallio-pon- 

 tile fibres); 3, efferent pal- 

 lial fibres to motor nuclei of 

 cranial nerves; 4, pyramidal 

 fibres (efferent pallial fibres 

 to motor nuclei of spinal 

 nerves); 5, pyramidal fibres 

 mingled with those of the 

 afferent (sensory) path; 6, 

 fibres of the lateral pons 

 system (occipitio-temporal 

 pallio-pontile fibres). The 

 various systems are not 

 sharply marked off as indi- 

 cated, but are more or less 

 intermingled. 



