THE VISCERAL AFFERENT DIVISION. 157 



which lie near the median plane dorsal to the central canal (Fig. 

 78). This column of cells and its central relations have long been 

 known in man and mammals but it is only in recent years that its 

 function as the center for sensory fibers of the sympathetic system 

 has been proved. The neurites from the cells of Clarke's column 

 go laterad to the surface of the cord and there turn cephalad to 

 form a well denned tract known as the direct cerebellar tract, since 

 it enters the cerebellum of the same side. As compared with the 

 cutaneous sensory system the visceral afferent system in the trunk 

 is very small. 



In the head, on the other hand, the visceral sensory surface is 

 greatly increased on account of the gills and there are present 

 special organs of the sense of taste whose fibers run in the same 

 nerves as the general visceral afferent fibers. The relation of 

 these organs and their fibers to the general visceral fibers is so 

 close that they may be spoken of as special visceral sensory struc- 

 tures. Because of the extensive branchial surface and the great 

 number of gustatory organs in the head, the combined visceral 

 systems may be larger than the cutaneous. The visceral afferent 

 fibers form usually the largest component of the X, IX and VII 

 nerves. They are distributed to the gills and the lining of the 

 pharynx and also to the mouth and the surface of the head and 

 body wherever taste organs are found. In fishes the ganglion 

 cells of this component in the vagus and glossopharyngeus are 

 situated in the epibranchial ganglia and the peripheral fibers reach 

 their destination by way of the branchial and pharyngeal rami 

 and the ramus intestinalis vagi. In the VII nerve the visceral 

 ganglion cells form a ganglion which in different classes of verte- 

 brates may be more or less closely in contact with the ganglion of 

 the VIII, the lateral line or the V nerve. The fibers enter the ramus 

 palatihus and other rami of the facialis which reach the mucosa 

 of the mouth and the gill of the spiracular cleft when that is present. 

 In cyclostomes this component of the VII nerve is very small 

 and its distribution has probably not been completely made out. 

 The general arrangement of these components in the cranial 

 nerves is shown in Figs. 51, 63, 79, 80. 



In amphibia and all higher vertebrates owing to the disappear- 



