66 Biillciin of Laboratoncs of Denisoji University. [Voi. xiii 



turn to take a longitudinal course parallel with and often almost 

 completely enclosing the spinal V tract. This secondary tract 

 is largely composed of small and feebly medullated fibers, so 

 that in Weigert sections it appears paler than the spinal V and 

 the other great longitudinal conduction paths of the oblongata. 

 Part of its fibers turn caudad and part cephalad. We therefore 

 have descending and ascending secondary gustatory tracts (trac- 

 tus gustus secundus descendens et ascendens) from both the 

 vagal and facial lobes. 



(i) Descending Secondary Gustatory Tract. 



In the carp, as shown by Weigert sections of the adult, 

 the descending tracts from both the vagal and facial lobes are 

 very extensive. From the facial lobe they constitute a massive 

 aggregate of medullated fibers in the "secondary vagus bundle" 

 complex. But the descending tracts from the vagal lobe are 

 largely unmeduUated fibers scattered through the substantia 

 reticularis grisea of the oblongata. 



The descending secondary facial tract arises, as in Amei- 

 urus, chiefly from the cephalic portion of the lobus facialis. The 

 fibers pass ventro-lateral to gather in a compact bundle mesially 

 and dorsally of the spinal V tract, farther caudad enclosing this 

 tract on all but its external aspect (Fig. 5, d.s. VII). There is 

 no obvious addition of descending fibers to this descending bun- 

 dle in the region of the lobus vagi. It can be easily distin- 

 guished from the ascending secondary gustatory tract from the 

 vagal lobe (Fig. 5, a.s. X) by the fact that the latter tract is 

 much more feebly medullated at this level. 



In the caudal part of the vagal lobe the motor zone is 

 greatly thickened as is also the substantia reticularis grisea, 

 which lies ventro-laterally of it and in intimate relations with 

 the layer of secondary gustatory tracts of the vagal lobe, the 

 descending secondary facial tract and the spinal V tract. This 

 whole area contains descending secondary vagal fibers. These 

 are chiefly very fine unmeduUated or feebly medullated fibers 

 passing from the layer of secondary gustatory tracts of the vagal 

 lobe caudad and mesad through the substantia reticularis grisea 



