Herrick, Gustatory Paths in Fishes. 



197 



mot. )(. r. 



Weigert sections show very clearly that fibers of the 

 motor roots of the vagus and glossopharyngeus arise not only 

 from the nucleus ambiguus but also from the motor layer of 

 the vagal lobe, as has been well known since Mayser. 



My GoLGi preparations very 

 rarely show good impregna- 

 tions either of the cells of the 

 motor layer or of the nucleus 

 ambiguus. The latter have the 

 form and arrangement which 

 have been often figured, the 

 main dendrites spreading out in 

 the substantia reticularis and 

 reaching the extreme ventro-lat- 

 eral border of the oblongata. 

 Other smaller dendrites spread 

 out within the nucleus itself and 

 the neurite usually springs from 

 the base of the main dendrite. 

 The dendrites of the cells of 

 the motor layer in some cases 

 spread out within this layer, 

 where they come into relation 

 with the radial fibers which enter 

 it from the layer of secondary 

 neurones. Others reach out into 

 the layer of secondary tracts and 

 into the substantia reticularis 

 (Fig lo), in both of which places they reach collaterals from 

 the secondary gustatory tracts. 



It appears that in no case do the peripheral motor neurones 

 come into direct relation with the peripheral gustatory neu- 

 rones, but at least one intermediary element is always inter- 

 posed. These elements may be the intrinsic neurones of the 

 vagal lobe, for short reflex arcs, or the chief secondary gusta- 

 tory neurones for more complex reflex connections reaching 

 beyond the vagal region of the brain. 



Fig. 14. Transverse section of the 

 vagal lobe of the right side of a young 

 carp, 5 cm. long. GoLGl method. 



X so- 

 Illustrating two intrinsic secondary 

 neurones of the vagal lobe whose 

 processes extend inward to reach the 

 motor layer, s.g.t., secondary gusta- 

 tory tract ; sp. V, spinal V tract. 



