652 



THE NEEVOUS SYSTEM. 



relationship with cells of the ventro-lateral nucleus. The fibres arising from this 

 nucleus proceed to the gyrus centralis posterior, and convey impulses to it, which 

 may excite a consciousness of touch, pressure, pain, heat, or cold. Some of these 

 spino-thalamic fibres enter the medial lemniscus in the medulla oblongata, but 

 others remain separate from it (Fig. 580) until they reach the level of the pons, 

 where they become added to the lateral margin of the bulbo-thalamic tract. 



[In Fig. 580 the line from the label "lemniscus medialis" points to the place 

 of junction of the spino- and bulbo-thalamic tracts.] 



Other groups of fibres, serially homologous to both the spino-thalamic and the 

 bulbo-thalamic tracts, come from the various sensory cerebral nerves trigeminal, 



Lateral ventricle 

 Nucleus caudatus 

 Corona radiata \ 



Corpus callosum 



Internal capsule 



Claustrunu 



Yhalamo-cortical (sensory) 

 radiation in internal capsule 



Tnsula 



Acoustic 

 , radiation enter- 

 ' ing transverse 



temporal gyri 



Ventro-lateral thalamic i 

 receiving the medial leu 



nd emitting sensory 

 fibres to the cortex 

 Acoustic radiation 

 Lateral geniculate body 

 receiving lateral lemnist 

 emitting acoustic radial 

 Lateral ventricle inferio 

 Medial geniculate body 

 'Fimbria 



cerebri 



Substantia -"'^"^JBBSSF^" """^SB^l "'"-.'Lateral lemniscus 



Cere n b?o*pinaland--' > " " P^K""^ Medial lemniscus at the part wh< 



cerebro-pontine tracts /4R^LSjBaj|^3 -^ffiM & ^the spino-thalamic and bulbo- 



inthepons jKliHBffl? Btt^ I thalamic tracts join 

 Nervus acusticus- 



Corpus trapezoideum - 



Pyramid 



Decussation of pyramids 

 Ventral cerebro-spinal tract 



FIG. 580. FRONTAL SECTION OF BRAIN, PASSING IN THE LINE OP THE CEREBRO-SPINAL TRACT (marked 

 in red] IN THE RIGHT HEMISPHERE (left side of Fig.), and on a more posterior plane in the left 

 hemisphere, where the sensory paths (tactile in blue, and acoustic in yellow) have been represented. 



facial, glossopharyngeal, and vagus and become added to the great strands that are 

 proceeding upwards to the thalamus (Figs. 5*79 and 494, p. 561). 



Of the other great ascending tracts in the spinal medulla, such as the two 

 pairs of fasciculi spinocerebellares, nothing further need be said ; nor is it necessary 

 to do more than remind the reader that from the nucleus dentatus of the cerebellum 

 a great tract (brachium conjunctivum) ascends to the opposite red nucleus and 

 thalamus, and through them establishes an indirect connexion with the cerebral 

 cortex in the precentral and frontal regions. 



The other sensory pathways to the cerebrum, auditory, vestibular, visual, 

 gustatory, and olfactory, are described elsewhere. 



The Corticifugal Projection Strands. The fasciculus cerebrospinalis, the great 

 motor or pyramidal tract, is composed of fibres which arise from giant pyramidal 



