I02 Bulletin of Laboratories of Denison University. [Voi.xiii 



rangement is probably merely a device for economy of space 

 (cf. Figs. lo and 30). (2) The deepest cells of the vagal lobe 

 are motor neurones (probably derived phylogenetically from 

 the underlying nucleus ambiguus and related to the dorsal mo- 

 tor nucleus of the vagus of Porel et al.) which supply directly 

 the intrinsic muscles of the palatal organ. These motor cells 

 are not present in recognizable numbers in siluroids or other tel- 

 eosts — correlated with the absence of the palatal organ. (3) 

 A large proportion of the intrinsic neurones serve as intermedi- 

 aries between the peripheral termini and the motor layer of the 

 vagal lobe, thus providing for a reflex connection within the 

 lobe between the taste buds on the palatal organ and the in- 

 trinsic muscles of that organ. 



The main paths of gustatory conduction in these fishes 

 may be summarized as follows (cf. the accompanying schemata, 

 Figs. 38 and 39.) 



A. Short Paths. 



1. Impulses originating in taste buds on the palatal organ pass by way of 

 the X and IX nerves to the vagal lobe; then through the intrinsic neurones to the 

 motor layer and the intrinsic muscles of the palatal organ (in cyprinoids only). 



2. From peripheral terminiin both the vagal and facial lobes to the substan- 

 tia reticularis of the same side via intrinsic neurones, the smaller type of margin- 

 al neurones (in cyprinoids) and collaterals of the chief neurones. These neurones 

 of the second order, either directly or through the mediation of tertiary neurones 

 of the substantia reticularis grisea, reach the dendrites of the visceral motor nu- 

 clei of the medulla oblongata. This provides a pathway for reflex movements of 

 the lips, barbels, tongue, jaws, gills and pharynx in response to gustatory stimu- 

 lation. 



3. Some of the chief gustatory neurones send their neurites directly across 

 the raphe, probably to end in the substantia reticularis of the opposite side of the 

 oblongata. There is also, of course, indirect connection between the substantia 

 reticularis of the two sides of the body, thus providing for coordinated action of 

 the muscles of both sides. 



4. The nucleus intermedins of the vagal lobes and the associated substantia 

 reticularis extend caudad from their lobes to fuse directly with important gusta- 

 tory centers lying raesially of the funicular nuclei — the inferior secondary gusta- 

 tory nuclei. These nuclei are connected by the commissura infima Halleri 

 and the commissural nucleus of Cajal is a specialized part of this gustatory cen- 

 ter. These nuclei are very intimately related to the funicular nuclei and thus 

 afford a mechanism of correlation between gustatory and tactile impressions. 



