362 



THE NERVOUS SYSTEM 



forated substance. However, the microscope shows cells scattered among the 

 fibres of the bundle and these cells probably represent the ganglion. 



The white substance of the telencephalon. A horizontal section through 

 the upper part of the trunk of the corpus callosum will pass above the basal grey 

 substance of the corpus striatuin. and. aided by the corpus callosum, each hemi- 

 sphere in such a section will appear as if consisting of a solid, half-oval mass of white 

 substance, bounded without by the grey layer of the cortex (fig. 620). As seen at 

 this level, the white substance of each hemisphere is known as the centrum semi- 

 ovale. Horizontal sections passing below the body of the corpus callosum involve 

 the corpus striatum and thalamus, and the appearance of the white substance is 

 modified accordingly (fig. 640). 



FIG. 642. OBLIQUE FRONTAL SECTION THUOVGH THE BRAIN IN THE DIRECTION OF THE CEREBRAL 

 PEDUNCLES AND THE PYRAMIDS. (Seen from in front.) (After Toldt, "Atlas of Human 

 Anatomy," Rebman, London and New York.) 



LONGITUDINAL FISSURE 



m 



SUPERIOR 



RADIATION OF CORPUS v 



CALLOSUM 

 SEPTUM PELLUCID I 



CHORIOin PLEXUS 

 OF LATERAL VEX- 

 TRICLE 



CORONA 

 RAH I AT A 



COLUMN OF . 



FORMX 



CHORIOID PLEX- 

 US OF TIIII:D 



VENTRICLE 

 INTERNAL CAP- 



SULE 



THALAMUS 



THIRD VENTRI- 

 CLE 



INTERPED UNCU- 

 LAR FOSSA 



INFER ion <'<>i;\T 

 OF LA 77.7,'. I L 

 VENTRICLE 



BRACHIUM PONTIS 



PYRAMIDAL I'Afi 

 CICULI OF PONS 



CEREBEL L I'M / 

 SUPERFICIAL FIBRES OF PONS 



BODY OF CORPUS CM.LOSUM 



AKTSKIOK llnl!.\- III' I.ATKRAL 

 VEXTSICL* 



HEAD HI-' I A I'D ATE 

 NUCLEUS 



RADIATION OF 

 CORPUS STRIA- 



EXTERNAL CAP- 

 SULE 



GLOB US rAI.LI- 

 DU8 



PYRAMID 



- FLOCCULUS 



GLO8SO-PBARYN- 



<;K.\I M'.i: 

 VAI.'US XKliVK 



J.\F/-:I:IOI: OLIVARY NUCLEUS 

 DECl'XSATIOX OF PYRAMIDS 



In the white substance of the cerebral hemispheres as a whole three main systems 

 of fibres are recognised: projection fibres, commissural fibres, and association fibres. 

 The projection fibres are those of a more or less vertical course, which pass to and 

 from the cortex of the hemisphere, connecting it with the structures below the con- 

 fines of the hemisphere. The commissural fibres are those of a transversely horizontal 

 course, which cross the mid-line and connect the two hemispheres with each other. 

 The association fibres are those which neither cross the mid-line nor pass beyond the 

 bounds of the hemisphere in which they arise, but instead connect (associate) the 

 different parts of the same hemisphere lobes with lobes and gyri with gyri. The 

 fibres which connect the cortex with the nuclei of the corpus striatum must be classed 

 as association fibres also, since these masses of grey substance are a part of the 

 telencephalon, while by definition those which connect the thalamus and hypothala- 



