CHAPTER VI. 

 X'iscERAL Afferent System. 



THE visceral afferent system, like the somatic, is repre- 

 sented in the cranial nerves by both general and 

 special subdivisions, of which the latter is concerned 

 with the sense of taste. Smell may also be included in this 

 category on physiological grounds, but its structural represen- 

 tatives are independent, whatever their phylogenetic origin 

 may have been. Both these components are represented in 

 each of the tenth, ninth and seventh nerves. Unlike the 

 somatic system, the two subdivisions of the visceral afferent 

 group end in the same column of gray matter according to 

 the account usually given. 



The sensory fibres of the glossopharyngeal and vagus 

 nerves upon entering the substance of the brain run in small 

 fascicles to a position between the dorsal end of the spinal 

 V nucleus and the ventro-lateral angle of the chief vestibular 

 nucleus. Here they take up a longitudinal, descending 

 direction, forming the fasciculus solitaritis, which runs down 

 to the beginning of the spinal cord (Pis. VI. -IX.). The afferent 

 facial fibres, which enter the brain farther forward, also run 

 back and slightly mediad near the dorsal edge of the spinal V 

 root and join the descending fibres of nerve IX. The fasciculus 

 is accompanied by two columns of gray matter, of which the 

 large one medial to it is the nucleus of the fasciculus solitarius 

 {nucleus fasciculi solitarii), while the one which lies ventro- 

 lateral to it is the nucleus parasolitarius. The former of these 

 has a very clear appearance and is a conspicuous object in 

 sections. Its anterior end is covered dorsally by the chief 

 vestibular nucleus, but it soon emerges and occupies a position 



